Indigo

Indigo (died May 2016) is a Coluan previously known as Brainiac 8. She was deemed the most dangerous prisoner ever sentenced to Fort Rozz.

Fort Rozz
Brainiac 8 was imprisoned on Fort Rozz for attempted genocide on Krypton and it was trapped in the Phantom Zone. After years of searching, she eventually found Kara Zor-El's pod. She took over the pod, causing the young Kryptonian to wake abruptly, noticing a computer console in her dashboard with a logo with three dots in a triangular shape, before Fort Rozz's engines activated and both of them escaped the Phantom Zone.

Indigo
Taking on the alias "Indigo", Brainiac 8 travels through the internet with the hopes of wiping out all humans on Earth. She tries to release private information about an infidelity website (DiamondDiscretions.com) to CatCo, but Cat Grant refused to release it. The monitors and other electronic devices start to go haywire at CatCo and the hacker (who was Indigo taking on a human face on-screen) tells Cat that since she ignored what was on the drive, there is going to be chaos in National City. She keeps to her word and all the lights in National City turn green, causing major car crashes. At Kara's apartment, Kara and James Olsen watch Winn Schott try to crack the hacker's code to no avail when the hacker appears on the screen and teleports through the computer into the room as a blue woman with the symbols of Brainiacs. She attacks Kara, and threatens to kill Winn and James Olsen, but Hank and Alex arrive and scare Indigo off. Later, Indigo teleports through another computer and meets with Non, where it's revealed that the two had earlier sexual encounters. Indigo tells Non that Astra’s notion of living alongside the humans can’t work, and says she'll do something to the human race so she and the Kryptonians will be only ones left on Earth. At the military site, Indigo uses General Mathers' cell phone as a means to enter the base. She swiftly kills/takes out the officers in the room, and reveals a stretching power to turn both activation keys. Kara arrives and fights Indigo. Indigo eventually traps her with her legs, but Kara escapes and goes after the missile. Realizing that anything she tries could destroy National City, she finally relents to consult Hank, who guides and helps Kara disarm the missile's tracking computer. Indigo, initially infuriated her initial plan failed, tries to send more missiles, but is knocked down by Kara. Kara dropped her phone during the landing (not seen on screen). After learning that Winn is working on a virus that will destroy her, Indigo uses the active device to reach Winn and choke him. Winn, though being strangled, continued to prepare his virus. Indigo begins to try to get Kara to back away, saying she (Indigo) is "invincible". Winn calls her a "glorified Windows Vista" and uploads the virus to Indigo. While she's being destroyed, she explains that if it weren't for her finding Kara's pod, none of them would have been on Earth at all. The virus finally consumes her, leaving no trace of her remnants.

Finally, Non, using the Omegahedron, shows that Indigo was not actually destroyed, with her body appearing on the computer board in severed pieces. Non says, "I merely broke your heart. Look what Supergirl did to you," and eventually says that he wants her to do things his way now.

Myriad
After Indigo was rebuild, Non finally executed his plan on Earth, beginning with National City and taking over the minds of all its residents via the program Myriad. As Alex Danvers and J'onn J'onzz return to the city to help Supergirl, Indigo is waiting for the twosome and lured them into a battle, with J'onn almost gaining the upper hand, she managed to attack him from behind and grabbing Alex. Indigo then orders a weakened J'onn to stand down or she'll kill Alex, and he does that, only to collapse a few seconds later. Then Indigo leaves triumphantly as she is convinced that J'onn, the last surviving Green Martian, has died. After she takes Alex to Non, Indigo suggests to use her in order to hurt Kara.

Death
Supergirl managed to broadcasts a speech throughout the city that helps the residents to break free, effectively ending Non's brief domain, so Indigo suggested to use the Omegahedron's signal to kill all the humans of Earth and leave Supergirl behind as the hero of a dead world. After discovering their plan, Supergirl and J'onn fly to Fort Rozz where they fight Non and Indigo. J'onn defeated the villainess by ripping her in half however, before she dies, Indigo reveals that she has locked the system to deactivate the signal in order to leave Kara and J'onn with no choice but to watch everyone on Earth die.

Powers

 * Cybernetic interface: Indigo is a Coluan cybernetic being. She is able to transfer body in the form of digital code and teleport through any technology by flying into it while in digital form. She can use any electronics as a portal to another destination, traveling through electronic and digital signals, while she is unable to travel through older broadcasting signals. She also could teleport only part of her body if she willed it, as she teleported her arm through a phone's screen, causing it to teleport out from Winn's computer and choke him. She can interface with any machinery and manipulate computer systems, as well as detect digital electronics and signals, while she could not do so with older broadcasting signals and technology.
 * Super strength: Indigo's strength allowed her to fight a Kryptonian on equal grounds.
 * Super speed: Indigo also showcased blinding levels of speed able to tackle Alex several feet into the ground in a blur of motion.
 * Invulnerability: Indigo's body is denser than a human's but not nearly as durable as a Kryptonian's.
 * Shapeshifting: Indigo can take the form of a blue athletic female or a blond human, the latter of which she only appeared as while projecting herself on computers or video screens.
 * Malleability: Indigo is able to manipulate her limbs to stretch and elongate to almost no limit and turn her fingers into claw like blades. It is later revealed that she can turn her limbs into blades that can pierce into Martians. In fact, she is able to absorb bullets harmlessly into her body if shot, as after being shot by J'onn J'onzz, the bulletholes vanished and she made the bullets rise out of her hand.
 * Flight: Indigo was seen flying down to meet Supergirl and J'onn J'onzz with Non beside her and when attacking Alex, she shot through the air in a blur of motion.
 * Self-repair: As a digital being, Indigo is able to self-repair, though she only if she is conscious, otherwise the Omegahedron can be used to reconstitute her, as Non did. Her ability to dissolve into digital code also allows her to scatter herself in minuscule particles and reform herself at will, as she did when thrown into an exploding structure by J'onn J'onzz.

Abilities

 * Expert hand-to-hand combatant: Indigo is an expert in unarmed combat, using athletic prowess to get the upper hand in a fight. Combined with her raw physical power, she was able to physically restrain Supergirl from behind with a grappling maneuver.

Behind the scenes

 * In the DC comics, Indigo, also known as Brainiac 8, is a descendant of the well known enemy of Superman, Brainiac. She was sent from a distant future era to infiltrate the superhero community, joining the team known as the Outsiders.
 * Indigo was portrayed by Laura Vandervoot, who previously portrayed Kara Zor-El in the television series, Smallville. This makes her the second character in the series to be played by a former Supergirl actress. The first was Helen Slater, who played Supergirl in the 1984 film, and recently made an appearance on the show as Eliza Danvers.