Frost


 * For Frost's host body and main personality, see Caitlin Snow.
 * For other uses of "Killer Frost", see Killer Frost (disambiguation).

"Killer Frost", originally labeled Khione after the Greek goddess of snow, is Caitlin Snow's alternate personality. Since a young age, Killer Frost existed within Caitlin due to cryogenic experiments performed on the latter by her father, Thomas Snow, in an effort to prevent Caitlin from suffering from ALS. However, Caitlin repressed Killer Frost for 17 years until her time with Team Flash, when Killer Frost began to reemerge. Originally Caitlin's Killer Frost powers mostly amplified her insecurities and anger, changing her chemical balance, but the further she continued to use these powers, the further she changed. Eventually, after defeating Savitar, Caitlin developed a special partnership with her Killer Frost side, going on to analyze her condition, which resulted in Killer Frost becoming a full-blown split personality, the actions of whom Caitlin would largely not remember.

In a battle against Clifford DeVoe, Killer Frost disappeared as a result of DeVoe using Dominic Lanse's powers to create a mental block which prevented Caitlin from accessing her alter-ego. After defeating Siren-X from Earth-X, Caitlin discovered that Killer Frost is still inside her, without the presence of dark matter.

After the team found out that Caitlin's father is actually alive, they discovered that he is also a cryogenic meta-human with an evil split personality, Icicle. During a battle with him, Caitlin is able to break through the mental block created, allowing Killer Frost to emerge. Cisco later gave Caitlin a mental activity dampener created by Harry Wells so she could communicate with Killer Frost. During a fight with Cicada, Team Flash discovered that Killer Frost is immune to his dagger (as she was not a dark matter-created meta) and could help defeat him.

Early life
Around 1999, Caitlin Snow's father, Thomas Snow, discovered that his daughter inherited his ALS gene. Desperate to save her, Thomas began performing experiments of cryogenic gene therapies on Caitlin in an attempt to freeze the disease, just as he had done with himself. While the experiments were successful, Caitlin began exhibiting a dual personality, whom Thomas called "Khione" after the Greek goddess of snow. During one such incident, Caitlin fell off her bicycle during an accident and got hurt as a speeding car approached, causing her second personality to fully emerge. Caitlin would repress this memory and Killer Frost for years.

Kidnapping Julian Albert
17 years later, Caitlin's Killer Frost persona would emerge periodically and gradually increasing in frequency as her meta-human powers emerged, especially when dealing with her estranged mother. She was kept at bay for a while after Caitlin used power-dampening cuffs to stop her powers, and subsequently her other persona, from emerging. After using her powers to save Barry Allen from Savitar, Killer Frost's personality came to the fore and she went to find Alchemy. She tortured one of Alchemy's acolytes to try to find him, but left him frozen just before CCPD arrived. She then kidnapped Julian Albert to make him run a search algorithm to find Alchemy, and eventually located another member of his cult. Julian managed to call the police, and the Flash arrived to try to talk Caitlin out of her Killer Frost persona.

She stabbed him in the leg and escaped to find Craig, the cult member Julian found. She threatened his family, and he told her that he didn't know where Alchemy was or who he was, but that he had shown them the future where she was Killer Frost permanently. Cisco Ramon and Barry arrived to stop her from killing the acolyte, and they fought. Unable to escape, Frost gave Barry a kiss to freeze him solid before being knocked out by one of Cisco's vibe-blasts. She woke up in the pipeline and tried to convince Team Flash she was back to her Caitlin personality, though they were unconvinced. After Wally West was cut out of the cocoon he was trapped in by Alchemy, Barry was forced to go to the pipeline to talk some sense into Caitlin. He let her out of her cell and asked her to kill him but, unable to hurt her friend, Caitlin managed to overthrow Killer Frost and regain control.

In early 2017, Caitlin was given a necklace by Julian that dampens her powers and also collects solar energy to charge it to ensure that it continues to work properly, thereby keeping Killer Frost at bay. After Iris West was touched by Clive Yorkin, who had the power to disintegrate anything he touched, she was slowly dying. Caitlin was then forced into using her powers to slow down and stop the disintegration. However, in the middle of this, Killer Frost briefly took control and stopped saving Iris. She even taunted Julian, who ended up talking her out of it and allowed Caitlin to regain control.

Joining Savitar
After S.T.A.R. Labs was attacked by Abra Kadabra, Caitlin was critically injured by shrapnel and helped Julian perform her surgery. However, she later began dying from a seizure. Julian, Cisco, and H.R. attempted to resuscitate her, to no avail. In an effort to bring her back to life, Julian ripped off Caitlin's necklace and her powers caused her wound to heal, but once she opened her eyes, it was Killer Frost who emerged. She knocked everyone back with a huge wave of ice and emerged from the icy smoke with her hair fully white. She then attempted to kill them with beams of ice from her hands, even knocking Cisco and H.R. by smashing a window they were behind. Julian then attempted to grab her necklace and put it back on Caitlin's neck, only for Frost to destroy it with another ice shot. He told her that he cared for her, and she used this to her advantage, telling him to kiss her so she could freeze his head. However, before they could meet each other's lips, Cisco knocked her back over a table and into a wall with a vibe blast. When the three men ran out of the room, Frost followed and found them attempting to hide in the pipeline. Just when she was about to kill them, Barry sped in and knocked her into a wall and told Caitlin that she could fight what was happening to her. She simply told him that she didn't want to and froze the doorway he was behind solid. When he searched the building for her, she was already gone. Later, while Killer Frost was walking through the woods, she came across Savitar. At first, she was startled until he told her not to be afraid of him as he wanted her to become an ally of his. She asked him why she should trust him and he revealed himself to be Barry Allen's time remnant. She then asked him what he needed her to do.

Hunting Tracy Brand
After joining Savitar, Killer Frost received a new suit and was sent to kill Tracy Brand at Central City University. When she arrived, Barry, Cisco and H.R. were already there trying to get her out. Frost entered by freezing and smashing a glass door and sending an icicle right for Tracy. However, before she could be impaled, Barry moved her out of the way with his super speed and told H.R. to get her out. He was then knocked to the ground by Frost's ice beam. As she was about to run after H.R. and Tracy, Cisco got in her way, she rubbed the fact that she was fully Killer Frost now in his face and shot him with an ice beam, knocking him over a counter and onto the floor. This was when Barry got up and used a flamethrower and his speed to launch fire at her, causing her to retreat. When she reported back to Savitar, he accused her of letting Barry and Cisco go on purpose and told her all she had to do to be a god like him is kill Tracy. She later showed up outside Jitters and was about to attack Tracy and H.R. again until Barry, Julian and Cisco showed up, allowing H.R. and Tracy to flee the scene. Frost chased after them by creating a path of ice that flew through the air with Barry chasing after her, attempting to get her to return to Jitters so Cisco could shoot her down. However, when she reached Jitters, Cisco couldn't shoot her down as he still saw her as his friend, and this gave her the opportunity to shoot a beam of ice at him, so Barry was forced to run in front of him and take the shot, sending him down a flight of stairs. Killer Frost then reached the ground again and walked over to Barry, taunting him. She then stabbed him in the leg again, stating "scar tissue is much more sensitive than regular tissue". After Cecille Horton left the West house, Frost grabbed her and threatened to kill her if her boyfriend, Joe West, didn't arrive at a certain address that Cecille was being held in. Joe attempts to pull his gun on her but is hit with an ice blast and thrown over an end table. Later, Team Flash arrived in a warehouse that Cecille was being kept in and Frost appeared out of the shadows and taunted Tracy about killing her and asking them to hand Tracy over in return for Cecille. Barry then attempted to talk to get Caitlin to snap out of it and let Cecille go but to no avail, she then reveals that she knows Cisco is hiding up in the rafters and sets off a bomb forcing him to quickly open a breach and land across the warehouse, knocked out and in a pile of boxes. Frost then went to shoot Joe with an ice beam only for Barry to run in the way and get frozen on the ground. Before Frost can do anything else, Cisco shot her in the back with a vibe blast. However, she quickly gets back up and the two shoot their respective powers at each other. At first, it seemed Frost was winning until Cisco mustered enough power to knock her back into a wall, knocking her out. Savitar then appeared and sped her out of the warehouse.

Regaining Savitar's memory
Since Savitar was a time remnant of Barry, he remembered everything that Barry did, so Team Flash wiped Barry's mind to prevent Savitar from knowing their plan. After they did this, Killer Frost wanted their plan to speed up and approached Savitar's kneeling armor in order to get to work only for him to abruptly stand and hold Frost against a wall by her throat. She asks what he's doing but he only asks the questions "who are you?" and "who am I?". She then realizes what's wrong and travels to S.T.A.R. Labs to get help from Team Flash. When Cisco, Wally and Julian return to the Cortex, Frost was waiting for them. Wally attempted to speed towards her but realized that he had lost his speed and she tells them that she knows why. The three were discussing with each other to see if they should trust her or not until Barry, Iris and Joe walked in, wondering why they looked so worried when Killer Frost walked out from Caitlin's old lab, causing Joe to pull his gun on her. Everyone told him to stand down and he did so. Barry, still in his amnesia like state, asked if Frost was some kind of supervillain, causing her to look at him with an "obviously" look on her face. He then left the room, which left Frost with former allies of Caitlin. She explains that what Barry remembers, Savitar remembers, and the team could just teach Barry everything and beat Savitar. However, there were lots of villains in Central City and no Flash to stop them at all. She then convinced them all that they needed to work with her to bring back Barry's memories. Cisco and Julian worked with Frost and while they worked, Cisco attempted to remind her of all of the memories they had working on the particle accelerator. It seemed to get through to Caitlin but Frost quickly took over again. Later, the three ran back to the cortex and turned on the TV, only to see that a building had been set ablaze by an infamous arsonist. Frost ends up helping Barry recover his memories and put out the flames. After everything had calmed down, she attempted to leave only to be stopped by Barry, Cisco and Julian. They tried to tell her that she was their friend and could be again with Julian also saying that he loves her, but she replied that she never loved any of them and entered the elevator. Once the elevator started its descent, Caitlin briefly took over only for Frost to bury her again.

Final fight
Killer Frost approached Savitar to ask what he was working on in his suit and he replied that his suit was damaged during his fight with Barry. Frost then asked if they were a team, referring to them both as "Barry and Caitlin". He looked up and replied that he wasn't Barry and she wasn't Caitlin. She then asked if Savitar was really going to kill Iris after all of the memories he shared with her. He asked if she is having second thoughts about their plan and she only shook her head, visibly scared. Memories begin to flood into Savitar's head and she asked what he saw. He explains that Barry went back in time to ask for Leonard Snart's help to retrieve the power source for their weapon to use against Savitar. Frost asked if she should stop them but Savitar just said that it doesn't matter. Later, Cisco got a vibe of Killer Frost in a forest, waiting for him to come fight her. Cisco then arrived at her location and the two began to fight only for Frost to overpower Cisco, flooring him and giving her a chance to kill him. However, before she could finish Cisco off, Savitar sped in and commanded her to spare his life. Confused, she asked why he needed to live. He explained that Iris had survived because H.R. had taken her place and died, and that they needed Cisco to build something for them. The three then speed back to Savitar's lair. Savitar explained to Cisco that he needed to convert the Speed Force bazooka into a quantum splicer in order for him to survive without the time paradox catching up on him. In order to make Cisco begin working, Savitar also threatened Frost's life, knowing that he would never get over the death of his best friend. After Savitar had left, Frost asked Cisco if he had finished the splicer and he nodded. He then attempted to tell her that if she continued to work with Savitar he would eventually kill her after he didn't need her abilities anymore, but she disagreed and thought they would always work together.

Right afterwards, Savitar returned to his lair. He asks if everything is done and Cisco explained that it is. Frost then began to raise her hands and Cisco repeated that Savitar would kill her but she doesn't listen and fires an icicle straight at his chest only for it to be stopped by a breach. The two villains looked shocked until Cisco's girlfriend, Gypsy, leaps into the lair through another breach and pulls Cisco into another one. Killer Frost asks Savitar if he cared that they escaped and he replied that it didn't matter since the splicer was ready. The two arrived at the outskirts of a forest and began to use the splicer to make sure Savitar would live, but they are stopped by Jay Garrick, who escaped from the Speed Force. They then turned to see that all of Team Flash had arrived. Frost told Savitar to go whilst she fought Cisco and Gypsy. She was quickly thrown to the ground which gave Cisco the chance to kill her but he refused and gave her a cure that was made by Caitlin's mother and Julian. She seemed very hesitant but once Savitar grabbed Cisco and was about to kill him, Caitlin Snow managed to take over Killer Frost and buried her instead and she saved Cisco's life. After Frost's defeat, Savitar was also erased from existence and Caitlin left soon after.

Working for Amunet Black
After this, Caitlin joined Amunet Black's criminal organization and worked in her club. Killer Frost also resurfaced to do jobs for Amunet and ended up becoming one of her favourite henchmen.

When Caitlin was working her shift in Amunet's nightclub, she was approached by Cisco who asked her to rejoin the team. She ended up accepting his offer and helped them get Barry out of the speed force. When she returned to the club to quit the criminal organization she confronted Norvock and told him about her decision. When he grabbed her by the arm, it caused Killer Frost to reemerge and she managed to bash his head on a nearby machine. She then threatened him and walked out of the club. She was about to go on a spree through Central City until Caitlin regained control and Frost was buried once again. When an alarm signalling an unauthorized breach went off in S.T.A.R. Labs, Killer Frost briefly attempted to take over Caitlin but was buried and wasn't able to take control.

Fighting Amunet
After Caitlin received a note from Amunet signalling her return, she attempted to get a plane out of the city but was invited by Iris and Felicity Smoak to go to Iris' bachelorette party. When they were sitting at a table in a restaurant, Norvock approached them and told Caitlin to go with him but she refused. He then displayed his meta-human ability, an eye-snake. He attacks everyone at the table and when Cecille, Felicity and Iris are all down, Killer Frost emerged and transformed in front of everyone's eyes. She then shot a beam of ice at Norvock which knocked him through a window. The women then return to S.T.A.R. Labs and they asked how Frost was still alive since they believed that Caitlin had gotten rid of her. Frost then explains that she is like a split personality and while Caitlin sleeps she is the one in control. She also retrieves her new suit from a large black bag and leaves to go and find Amunet Black. When she reached Amunet's club, Frost threatens her bodyguards to get past them and is greeted by Amunet herself. The two women and Norvock then enter a back room where Amunet kept a meta-human hostage and used his psycho-active tears as a drug. She then asked Killer Frost if she wanted to rejoin her and they could run Central City together as gods. Frost, however, refused Amunet's offer and the two prepared themselves to fight each other until Iris ran in between them and managed to get Killer Frost out of there and back to S.T.A.R. Labs. The girls asked Frost how she knew Amunet and she explains that she and Caitlin both worked for her and actually ranked very high in her criminal organization. Frost then told them that she planned to retreat to another Earth to escape Amunet and live her own life how she wanted, without Caitlin. Iris then attempted to talk Killer Frost out of leaving and told her that she and Caitlin could live together as one. However, Frost only threatened to freeze her hand off and leaves the room to go fight Amunet. The two women meet under a bridge. Frost didn't expect to see Amunet herself and was caught off guard when she launched a large piece of metal into Frost's shoulder. She then attempted to recover by launching ice blasts at Amunet but she only deflected them with a metal shield and launched two more large pieces of metal that floored Killer Frost. Amunet then picked her up by the collar of her jacket and started to throw punches that made Frost retreat back into Caitlin's mind and allowed Caitlin to retake control of her body. Caitlin then returns to S.T.A.R. Labs and decided to stay while Iris, Felicity and Cecille fought Amunet. However, when things went south and Felicity and Iris were captured, Caitlin appeared in front of Amunet and her henchmen and allowed Killer Frost to take control. As Iris and Felicity ran behind Frost, Amunet ordered her goons to kill them but before any of the bullets could hit them, Frost made a giant igloo-like ice object to protect them. Iris then told Cecille to turn on a giant magnet so Amunet couldn't use her powers. She did as Frost had instructed, and rendered Amunet powerless. Frost then formed an icicle, ready to stab and kill Amunet until Iris managed to talk her out of it and they all return to the lab. Later, the boys from Barry's bachelor party arrived back in the lab to find Killer Frost waiting for them in the cortex. They are shocked to see her at first but she slowly transformed back into Caitlin and explained to them what was going on with her. After this, Caitlin and Killer Frost began working together and Frost became a fully fledged member of Team Flash.

Crisis on Earth-X
During Barry and Iris' wedding, the priest was killed by Nazis from Earth-X. Cisco then told Caitlin to let Frost out and when she did, Mick Rory noticed her and took quite a liking to her. Frost created a giant icicle around her hand and killed a few Nazis on the aisle of the church. She then reappeared to fight the Dark Arrow but was ultimately overpowered by him and thrown against the wall of the speed lab. Caitlin, Cisco, Harry and Dinah Drake were locked in the pipeline by the Nazis but were all freed when Iris and Felicity found them and opened their cells. A robot from Earth-X attacks S.T.A.R. Labs, and everyone present from Team Arrow, Team Flash, and Team Legends teamed up and destroyed him. Later, in the final battle, Frost uses her ice path ability to fly herself, Amaya Jiwe and Zari Tomaz up to the Earth-X version of the Waverider, the Wellenreiter, and destroy it. After the Nazis are defeated, Barry, Iris, Felicity, and Oliver Queen all get married and the heroes return to their respective Earths and times.

Battling The Thinker
After Barry was wrongfully accused of murdering Clifford DeVoe, he was in his trial when the city was threatened by a meta-human Cisco nicknamed Fallout. Killer Frost was needed to cool him down or else the entire city would be nuked by him. Cisco and Harry Wells had to traumatize Caitlin in order to get Killer Frost to emerge and when she did, she and Cisco were breached to Fallout's location. At first, Frost seemed to have won by simply freezing Fallout, but he broke out of the ice and shot Frost with a beam of energy, sending her flying back into a bus stop and also knocking her unconscious. Fallout was then defeated by Barry and Cisco.

Killer Frost helped Vibe when they were sneaking into Trickster and Prank's hideout. When they both saw what appeared to be hostages, they ran towards and began to set them free until they heard a noise behind them and saw a group of Beebo toys that Frost froze and shattered with her powers. When they turned back to the hostages they revealed themselves as Trickster and Prank in disguise and put power-dampening cuffs on Frost and Vibe, causing Killer Frost to disappear and Caitlin to reemerge. Both Caitlin and Cisco were then saved by the newest member of Team Flash, Ralph Dibny.

When Ralph began to doubt himself, Caitlin went to his office to try and give him a pep talk but when he wouldn't listen she let Killer Frost out and she talked to him. He told her the problem was that he believed all of his friends would leave him as his friends in the past have. Frost then told him that the people in Team Flash never gave up on her and that they would never give up on him, which lifted his spirits. He even called her "Frosty Oprah". When Barry Allen attempted to escape from prison because of Amunet who was looking for meta-humans to buy and recruit into her organization, Vibe and Killer Frost breached into Iron Heights and asked him to come back to S.T.A.R. Labs with them, but he refused, not wanting to become a fugitive. Clifford DeVoe was also alive and took over the body of former Team Flash enemy, Becky Sharpe.

Veronica Dale and a nuke
When the team heard about an attack on the CCPD at an airfield, Killer Frost, Vibe, The Flash, and Jesse Quick traveled there to help them. Once they arrived they were able to quickly take out the henchmen and were ready to take out their boss, Veronica Dale, until she revealed that she was about to activate a nuke. However, before it destroyed all of Central City, Barry and Jesse entered Flashtime and attempted to figure out a way to deactivate the nuke. Jay Garrick also came from Earth-3 to try and help them. Eventually, the three speedsters thought it was a good idea to cool down the nuke and went to take Killer Frost into Flashtime. Once in motion with the speedsters, they brought her into the container where the nuke was located and attempted to send a beam of ice to cool it down, however, Frost began to burn up and her powers had no effect on the bomb. In order to stop Frost from burning up, Barry puts her back into normal time. Barry ends up taking Iris' advice and stops the nuke from destroying the city with help from the Speed Force.

Disappearance
Team Flash came up with a plan to attack DeVoe head on and enter his pocket dimension. Killer Frost, The Flash and Vibe then prepare to enter the pocket dimension and defeat him. However, when they arrive, they realize that he wanted them there so that he could attack S.T.A.R. Labs with no issues. Harry, Joe and Iris were all attacked by DeVoe and his wife, Marlize. Iris was able to bring the three back and they attempted to fight DeVoe but he ended up killing Ralph and stealing his body. He then knocked Barry and Cisco back and when Frost attempted to stab him, he stole her powers and appeared to kill Killer Frost as well. He then knocked Caitlin back into a wall, unconscious. Caitlin later got tested by Cisco and Harry and they were both unable to find any trace of dark matter in her body.

After Team Flash defeated Siren-X, the Earth-X doppelgänger of Laurel Lance, Caitlin found out that Killer Frost is alive but without any dark matter in Caitlin's body, she is unable to appear. The team began to help Caitlin to try and get Killer Frost to reemerge, they ran tests that involved Cisco shooting her with his vibe blasts, which caused nothing to happen. However, while Barry and Cisco are fighting DeVoe, Caitlin appeared and used Leonard Snart's gun on DeVoe in an attempt to get Killer Frost to return, but to no avail as he almost killed Gypsy.

Still desperate to get Killer Frost back, Caitlin finally went to Amunet for help. She led the team to believe that they needed Amunet to help defeat DeVoe and they all managed to get her to help them. Caitlin then struck a deal with her and told her that if she could get Killer Frost back she would do one favor for her. However, it's revealed that Amunet didn't know how to bring her back but still gave Team Flash an item that could help defeat DeVoe.

When Caitlin went to therapy with Dr. Finkel, she revealed that Caitlin had been repressing a memory from her childhood, a memory which was very traumatic for her. She later asked Cisco to vibe her to this memory and see what happened only to see her younger self get hit by a car and then transform into Killer Frost. This revealed that Frost had been inside Caitlin even in her early childhood, before the particle accelerator explosion.

In the final battle against DeVoe, when Cecille went into labor, her powers which she received from her pregnancy kicked in and Killer Frost briefly inhabited her body. She grabbed Caitlin's arm and told her that she had found Thomas and he had been that way all the time.

Defeating Icicle
Team Flash had discovered that Caitlin's father's death certificate was a fake and that he was actually alive. Barry, Caitlin and Cisco eventually tracked him down to a warehouse owned by Tannhauser Industries. However, it was later discovered that he was also a cryogenic meta-human that had an evil split personality that attacked the team. The personality wanted to use a serum, that Caitlin reluctantly created, to kill off Thomas for good and inhabit the body himself. Just as he was about to inject himself, Caitlin managed to break through the mental block that DeVoe had created, allowing Killer Frost to emerge and shoot him back with an ice blast. He quickly attempted to convince Frost to take the serum as well and work with him but she refused, stating that Team Flash was her true family. As she walked towards him, she stood on and destroyed the serum. She created an ice-fist and began to punch him but stopped as Thomas' personality emerged and spoke to Caitlin. This turned out to be a short reunion as the evil personality reemerged and shot her with an ice blast, proceeding to use two ice blasts to launch himself into the air and escape. Later, Caitlin discovered that she could use the cerebral inhibitor to speak to Frost through the mental block and the two began to catch each other up.

Meeting Cicada
During Thanksgiving, Caitlin, Cisco and Sherloque Wells decided not to attend the party at Barry and Iris' apartment, causing Killer Frost to emerge. She questioned they're decision of eating by themselves instead with friends who care about them and proceeded to walk off to the party, asking if they were coming or not.

During a battle with Cicada, the entire team was taken down by him and just as he was prepared to stab Barry with his dagger, Killer Frost emerged and fired an ice beam at him, sending him flying into a nearby van. He quickly stood and escaped the scene. The team later realised that Frost is immune to Cicada's dagger and could be useful in defeating him.

Elseworlds
Killer Frost and Elongated Man were sent to Ivo Laboratories to help deal with A.M.A.Z.O., who had been accidentally activated by an inexperienced Oliver Queen using Barry's speedster abilities. The two and Officer Jones were unfortunately not strong enough and as they were floored by the android, it absorbed the two meta-humans' abilities, using Frost's abilities to fly through the roof and escape.

After travelling to Gotham City, Kara Danvers used Caitlin to gain access to Arkham Asylum, convincing the nurse that she was a mentally ill meta-human, even quickly flashing Frost's eyes. After they got inside, a riot began and the two split up. Eventually, Caitlin came across a frantic Nora Fries who was searching for something amongst the shelves. When Caitlin attempted to help her, Nora blasted a beam of cryogenic smoke at her, causing Killer Frost to emerge and engage in a fight. When Nora grabbed her husband's cryo-weapon, Frost asked for some assistance over her comms but before Barry or Oliver could arrive, Nora blasted her back through a table, knocking her unconscious.

Sabotaging the cure
Whilst Caitlin was stitching up Cisco's hand wounds, Killer Frost briefly emerged in order to freeze the wounds. Later, after Cisco began working on the meta-human cure, Frost appeared behind him and destroyed his work with a freeze blast. When asked what she was doing, Frost simply stated that a meta-human cure was not needed and that her and Caitlin were doing fine together. However, Cisco explained that he wanted to cure all those who did not ask for their powers, including himself, who wanted to grow old with someone and have a normal family. When Weather Witch and Silver Ghost were partaking in a dangerous joyride in Central City, Nora recruited Killer Frost for help. Frost created a giant ice wall in the road that, unfortunately, didn't stop the two as the car they were driving was able to phase through the wall. After the two ultimately escaped, Nora asked Frost if she was the one behind the car's control loss, to which she was confused.

After Caitlin supported Cisco's decision and began working on the cure as well, Frost then emerged and destroyed her work as well, much to the shock of Ralph, just as Barry walked in needing help on a mission to protect meta-humans from Cicada. Frost suggested they start looking in Amunet's abandoned club where they discovered a distraught Norvok using the club to hide out in. The group informed him on the situation and asked if he wished to help them save the other meta-humans, which he agreed to. After one meta began to go against the plan, Norvok informed her of a fellow meta-human's death at the hands of Cicada, being so distraught, he left the room with Frost following closely behind. When they were alone, Norvok explained his past of working at the Central City Zoo, where he obtained his abilities and the reason he only looked out for himself. After he left, Ralph sat to speak to Frost and asked if she was just as afraid as Norvok, about losing Caitlin. Before she could respond, Barry returned with another meta-human but left again to track down Peek-a-Boo.

Later, Frost and Ralph finished their heart-to-heart as she explained how afraid she was that Caitlin would one day grow tired of her and take the cure herself. Norvok then entered and announced that it was time for the meta-humans to leave, however, before the chopper could take off, Cicada appeared as Ralph attempted to get the metas to safety. Barry and Frost both stayed in order to fend Cicada off but Barry was ultimately unsuccessful, being launched into a large pile of crates, unconscious. Frost then fought Cicada head on, even being able to draw blood by cutting him with an icicle, however, he managed to generate a large blast, knocking her backwards, causing her to be disoriented. Just as his dagger was about to hit Frost in the back of the head, Caitlin psychically warned her, allowing her to swiftly dodge the weapon with ease and also freeze it long enough for Barry to gain back his powers. However, Cicada managed to escape into hiding with Team Flash believing he would stay hidden for a while longer. After Caitlin resurfaced, Frost gifted her with an apology and also a crucial piece needed to complete the meta-human cure, Cicada's blood.

Multiple deaths
After Iris experienced a run-in with Cicada on his property, Barry, Ralph and Frost all rushed to her aid. Once they arrived, he was gone but Iris exclaimed that she knew how to inject him with cure as she had discovered his weakness.

Cicada later managed to kidnap Iris and hold her hostage on a rooftop, worried for her mother's life, Nora rushed Frost to the location and Frost immediately created two icicles ready to fight. However, she did not notice Cicada's dagger behind her and it ultimately stabbed her in the back, killing her. Desperate to help, Nora ran back in time and ran back to before Iris was kidnapped, when Frost and Caitlin were both alive. After resetting the timeline 52 times, failing to save each Team Flash member, Nora finally let them help her come up with a plan to make sure no one died. As Iris and Nora distracted him, Frost, Ralph and Cisco all appeared on the roof and shot at Cicada but before the dagger could hit one of them, Nora briefly reversed time and made it stab Cicada instead, forcing him to retreat.

During Gorilla Grodd's return, Caitlin and Cisco's minds were both controlled by him. After Cisco was locked in the pipeline by Barry, he witnessed Caitlin giving Grodd a device he used to enhance his psychic abilities, however, before he could pursue the Gorilla, Frost emerged and shot Barry with an ice blast, allowing Grodd to escape.

Meeting the New Cicada
When the Team learned of Cicada's plan to murder his next target, Philip Master, Frost managed to quickly be breached in and switch places with Master, catching Cicada by surprise and giving Barry time talk him down. When Frost returned to S.T.A.R. Labs, Nora asked how long the dagger would be out of action and she explained that Barry would only have around 60 seconds. When Barry eventually failed and was beaten, Frost quickly breached back to the alley and attempted to knock Cicada out only for him to escape once again. Later, the team managed to get him to the lab and talked him into taking the cure. However, during his surgery by Dr. Vanessa Ambres, S.T.A.R. Labs' power suddenly shut down and a seemingly new Cicada broke in and attacked the team. They all attempted to battle her but were all immediately defeated as she took the original Cicada back to her lair, murdering Dr. Ambres in the process.

Icicle's return
After Icicle attacked Tannhauser Industries, he also kidnapped Caitlin and her mother, placing power-dampening cuffs onto Caitlin's wrists to prevent Frost from emerging. However, when he hit Caitlin with an ice blast, it also froze her cuffs, shattering them and setting Killer Frost free. When she confronted him, he had already placed her mother in a freezing chamber and then quickly fled. When Barry arrived, Frost instructed him to save her mother and she set off after Icicle, the two of them creating separate ice paths to take flight on. Eventually, Frost managed to shoot him off his path but he also managed to ambush and stab her in the shoulder, forcing Killer Frost back and bringing Caitlin out. However, before he could kill her, Thomas overtook Icicle and was reunited with his daughter. Tragically, the reunion was short lived as Cicada quickly showed up, focused on killing Frost only for Thomas to sacrifice himself to save his daughter. He then died in Caitlin's arms as his wife watched on.

Still grieving from Thomas' death, Killer Frost remained in Caitlin's mind and barely ever emerged. While Caitlin and Ralph were visiting the Tannhauser research lab, he eventually talked her into coming out and freezing up a hole in the roof, cursing him in the process.

Defeating Cicada and Reverse Flash
After the team had discovered Cicada's plan of releasing a virus into the city to wipe out meta-humans, Killer Frost, Barry, Ralph and Cisco managed to ambush her at CCPD and render her unconscious. While Cisco deactivated the device, Frost, Ralph and Barry did their best to distract her but the three of them were ultimately defeated. However, Cisco eventually deactivated the device and knocked Cicada to the ground just as Frost threw the mirror gun Barry's way. As Barry shot the gun, Ralph screamed for him to stop. Ralph ended up jumping in the way of the gun, causing his body to uncontrollably misshape, giving Cicada time to escape. The team later tracked down her lair and devised a plan to administer the cure to young Grace so that Cicada would cease to exist. Once they reached the lair, the team breached Cicada back to S.T.A.R. Labs in order for Nora to speak with young Grace and by the time she does, Cicada had already returned and was about to kill Nora just as Barry shot the dagger. She then began to be erased from existence and the team briefly believed they had ended it but didn't realise that their actions had just set Eobard Thawne free.

After Barry and Nora were defeated by Thawne, the rest of the team breached by their side and he greeted them individually, including Frost. They all then managed to use their individual abilities to overpower Thawne and ultimately defeated him. However, he ended up escaping after Barry realised that their actions had caused Nora to be erased from existence as well. Later, Cisco ended up taking the meta-human cure but didn't leave S.T.A.R. Labs without gifting Frost with something, a new suit.

Altered reality
After John Deegan used the Book of Destiny to rewrite reality and made himself "Superman", Caitlin and Killer Frost's lives were rewritten. It appeared that Frost had fully taken over and worked under Deegan as one of his prime soldiers. After he returned to his base, Frost and John Diggle applauded his actions but he quickly made them stay quiet and exclaimed that the Trigger Twins had escaped him. Diggle and Frost quickly assured him that they would be captured just as a warning from the pipeline alerted the room. Frost explained that it must have been "Subject 1" but "Superman" quickly explained that he would take care of her himself.

Later, Frost travelled down to the pipeline to speak with Agent Danvers and asked her to go home but became skeptical when she refused. She asked if she had boyfriend trouble but Alex just explained that she thought the work they do is important and she wouldn't change. Frost simply shrugged and left the pipeline. After Kara had managed to get through to Alex, the two attempted to escape Deegan's base but were confront by him, Frost and Diggle. However, a breach opened and Barry, Oliver and the real Superman came through and the two supermen broke through the ceiling and began their fight whilst Diggle and Frost fought Oliver in the elevator. The two were ultimately beaten by him and thrown in the pipeline. This reality was later returned back to normal after Superman used the Book of Destiny to repair it.

Personality
"Right, I'm the queen of letting these people down. But you know what? They're still here. No matter how much I disappoint them, they still show up for me.  I don't really understand it, but I think that's part of this whole friends thing.  So, unless you do something worse than kidnap and stab them, I think you're gonna be just fine."
 * -|Present=

- Killer Frost to Ralph Dibny

Worrying about her new-found, uncontrolled powers, Caitlin's emotions become heightened enough that she became a vindictive, angry and cruel individual, similar, but not identical to Frankie Kane's split personality disorder. Also like Frankie, when affected by her powers, her eyes glow pale blue (while Frankie's glow pink). However, while Magenta tried to get rid of the Frankie persona altogether, Killer Frost state amplifies Caitlin's own fears, insecurities and bitterness. As Killer Frost, she mocked Barry by mentioning his most horrible failures including the deaths of his mother, father, Eddie and Ronnie, as well as revealing to Cisco that his brother, Dante was alive in the pre-Flashpoint timeline, before Barry changed it. She expressed bitterness over Barry only caring about himself and his own happy ending, while she was left broken.

Caitlin also mocked Cisco by calling him pathetic for feeling sorry that he had to hurt her to save Barry. She openly blamed Barry for what's happened to her, yet admitted that she feels broken. She nearly killed Julian and one of Alchemy's Acolytes, however, she was still unable to kill Barry, making her snap out of her anger, as she became horrified at what she almost did.

Once Killer Frost was fully awakened due to Caitlin's temporary death and revival, she states that she doesn't want to be cured and wants Caitlin never to come back. She allies herself with Savitar after he reveals himself to her.

Killer Frost went after Tracy Brand after Savitar promised that if she lives up to her name and murders Tracy, she could be a god. She arrived at CCU in her new outfit and attacked Barry and Cisco, but when Barry fought back with fire, she ran away. She then attacked Tracy for the second time outside Jitters and continuously formed an ice slide that she slid on for a while without any difficulty. She took advantage of the fact that Cisco would not hurt her and almost hit him with a blast that Barry took. She stabbed Barry in the leg so that he couldn't follow her and she left, claiming that this is her now.

Later, Killer Frost kidnapped Joe's girlfriend Cecille outside of Joe's home and threatened to kill her if Joe and the team did not hand over Tracy to her and Savitar. Later at the supposed exchange site, she claimed that killing Cecille would bring her no joy but Tracy's death at her hands would. When Barry tried to talk her out of it, she knew exactly what Barry was going to say. She and Cisco later faced off, and while she seemed calm at first, she later fought back as hard as she can and lost to him. Cisco managed to get a sample of her blood, which could be the key to making a cure for her. Before Cisco can take her, Savitar arrived and took her away.

Despite all this, while reluctantly working alongside her former allies, it was shown she still has a strong attachment to her memories of working at S.T.A.R. Labs when she and Cisco reminisced about Ronnie losing his temper back when they were trying to build the particle accelerator. However. Killer Frost also showed in this moment that thinking about who she used to be made her uncomfortable as she quickly, sullenly, stated that she didn't want to stay any longer than she had to. Her conflicted feelings about herself and her old allies were again emphasized when she told Team Flash she never loved them and left, only for the assertion to hurt her heart enough to cause the real Caitlin to emerge for a few seconds once she was out of the team's sight.

Despite her continued allegiance to Savitar, Caitlin began showing signs of regret and doubt in her betrayal. During the final confrontation of Team Flash and Savitar, Cisco's unceasing loyalty for Caitlin finally enabled Caitlin's true-self to become permanently restored and reconciled with her friends. At the same time, she felt lost, unsure of who she is now.

Six months after Savitar's defeat, Killer Frost became stronger and eventually was able to regain control on various occasions. Recently Killer Frost's personality has become similar to Caitlin's, after Iris convinced Killer Frost and Caitlin that they could co-exist they decided to be allies and not enemies. Killer Frost has also become close with Team Flash, growing to appreciate their willingness to never give up on her despite her mistakes. She even assured Ralph Dibny that his friends will always be there for him when the latter briefly lost his confidence after failing a mission.

In the future in which Iris dies, by the time of the year 2024, Caitlin has become too far gone to the point where she refuses to be called real name, as she prefers being called by her alias "Killer Frost", she becomes angry when people call her by her real name, despite her insanity and cold nature, Caitlin is very observant, she was able to realize that the Barry Allen she was speaking to was the younger-self of her Barry; due to the look on his face, as the latter had not yet become emotionally broken, as his Iris was not dead yet. This future was later erased when Savitar killed H.R. instead of Iris; albeit by accident.
 * -|Erased future=

Powers

 * Meta-human/Cryogenic physiology: When Caitlin's father, Thomas Snow, learned that his daughter inherited ALS, using his cryogenic research, Thomas cured Caitlin of her disease, but also granted her new-found powers. They remained dormant for years (apart from a few brief episodes during childhood) as several tests never showed signs of a meta-gene. Three years after the S.T.A.R. Labs particle accelerator explosion, Caitlin's powers finally emerged fully.
 * Energy absorption/Cryokinesis: Killer Frost's powers work by absorbing all existing heat around her, thereby reducing the temperature and to freeze targets well-below negative 370 degrees, even shattering beings as powerful as the Black Flash. Furthermore, her powers can reach such low levels that they can completely negate a speedster's healing powers and alternatively neutralize accelerated decomposing. Killer Frost can create various ice structures with ease, even creating large bullet proof shields that can withstanding point blank automatic rifle rounds, as well as launching upon manifestation sharp projectiles in rapid succession, creating an icy blade around her arm or as means of transportation, by producing icy waves of such propulsive strength, with one hand behind her, to propel herself forth across an ice slide she forms before her with her other hand, similar to Firestorm's fire-based propulsion ability. Her powers can also affect the weather around her, dropping the climate of the area and cause it to snow. She can also freeze objects without direct contact shown when she froze H.R's coffee from afar. A tell-tale sign of her accessing her powers is producing icy mist from her hands. As displayed by DeVoe, however, it would appear her ability to absorb energy may have been a power that developed as a result of her exposure to dark matter from the particle accelerator.
 * Freezing kiss: Killer Frost is able to freeze people through a kiss, as shown when she went up against Barry but was stopped by Cisco.
 * Freezing breath: Killer Frost is able to create a fog with her breath. Around six months following the defeat of Savitar, Killer Frost, grew powerful enough to orally produce cold mists with enough momentum to knock several people backwards and off their feet.
 * Cold immunity: Killer Frost exhibits a high resistance to frigid temperatures. She is shown to be able to hold the ice constructs she manifests with little trouble. She was also seen unaffected by a snowstorm she created after escaping S.T.A.R. Labs.
 * Accelerated healing factor: As Killer Frost, she can endure more grievous injuries and likewise heal much faster than even a speedster, though foreign matter must first be taken out to not impede the healing. After clinically dying from a combination of a seizure and her reopened impalement wound, she was immediately resuscitated into a stable and cognitive state while her wound seamlessly healed completely in seconds. However, her healing powers only work when her Killer Frost side takes over, as wounds inflicted by Amunet left bruising and required stitches. Interestingly enough, Caitlin's Earth-2 doppelgänger lacked this aspect of their near-similar meta-human powers, which was what led to Earth-2 Killer Frost's death at the hands of Zoom.

The Flash
{{Scroll|

Season 5
}}

Trivia

 * Killer Frost's original name was Khione.
 * Unlike Caitlin, Frost despises the color pink and hates wearing it, preferring to wear blue.
 * Frost has a drink named after her at CC Jitters, the Killer Frost drink.
 * By, both Frost and Caitlin can talk to each when either of them is in control, showing an acceptance that both them share the same body.
 * According to Caitlin, both she and Frost enjoy the 1985 film The Breakfast Club. She stated that Killer Frost loves the character John Bender.
 * Since the Meta-human cure works by removing the dark matter from the subject's system, it won't have any effect on Killer Frost.