- "Did you know that rubies are one of the toughest gemstones?"
"Only diamonds are tougher."
- —Alex Danvers and Ruby Arias on Ruby's name[src]
Ruby's mother, Samantha Arias, who was unknowingly the human alter-ego of the Kryptonian Worldkiller "Reign", became pregnant with her to a human father at the age of 16. As a result, Samantha was kicked out of the house by her adoptive mother, Patricia Arias. According to Selena's hologram, carrying Ruby also delayed Samantha's development into Reign.
At one point, Ruby moved with her mother to Central City when Samantha received a job there and was mad that she had to leave her friends behind in the middle of the school year. Due to them moving, Ruby and her mother had to spend Christmas in a truck stop motel at Route 34. At the motel, the duo had a snowball fight in the parking lot and made a Christmas tree out of newspapers. That night, they slept in an "awful" bed that smelled like moth balls. Despite the negative sides of the trip, Ruby affectionately remembered it as her best Christmas since she and her mother were together.
The unveiling and her mother's powers
In late 2017, Ruby and her mother went to the Supergirl statue unveiling at the waterfront, where Ruby bumped into Alex Danvers as she rushed to the front of the crowd. Samantha asked her to properly apologize, which she did. Alex accepted and Ruby ran off, excited to see the statue. During the unveiling however, there was an attack at the waterfront, creating dangerous earthquakes. Ruby became lost in the confusion and as she desperately looked for her mother, another tremor caused a metal tower to fall, pinning Ruby down. Ruby screamed for help, and Samantha, frantic and desperate to save her daughter, was able to lift the bar off, much to her and Ruby's shock.
Afterwards, Samantha put this feat down to an adrenaline rush but Ruby began to believe that her mother had powers like those of Supergirl.
A week later, Ruby's mother cooked the two of them breakfast before driving her to school. Ruby explained she needed to be picked at 5:30 pm due to a book event. Samantha reminded Ruby that Mrs. Queller would do so since she was booked with meetings all afternoon. Ruby was left slightly downcast at the change. Partway through the day, Ruby claimed to her classmate, Stephanie Harrison, that her mother had superpowers, but Stephanie dismissed her as a "liar". Angered, Ruby punched Stephanie in the face and was subsequently sent to Principal Coburn's office. As punishment, Ruby was suspended from school for the rest of the day. Samantha came to pick her up, annoyed that she had to leave work early on her first day because of Ruby's carelessness.
Back at home, Samantha and Ruby discussed what happened. When Ruby brought up the possibility of her mother having powers based on the waterfront incident, Sam immediately dismissed the notion, much to Ruby's frustration. An argument ensued, in which Ruby claimed her mother should admit to and accept her extraordinary nature. Losing her temper, Sam angrily shouted that she was just a normal mother with a normal kid. Upset, Ruby felt her mother also believed her to be a liar and stormed off to her room.
Later that day, Ruby snuck out and went to Stilton Pizza for dinner to clear her head, ignoring a text from her mother. Shortly after, Psi launched an attack outside while robbing a bank. Getting an idea, Ruby texted her mother back with her location and an SOS message before walking straight into the crossfire, hoping that Samantha would save her with superpowers. When Ruby was nearly crushed by some falling rubble, Samantha arrived and rushed to her side. Just then, a wrecking ball broke off from a truck and plummeted towards them but Supergirl intervened, catching the wrecking ball and moving it aside.
Following the ordeal, the pair recovered in the back of an ambulance. Alex checked on them and recognized Ruby. The two talked about Ruby's name and the fact that rubies are one of the strongest gemstones, second only to a diamond, which cheered Ruby up. After Alex left, a contrite Ruby accepted that her mother didn't have powers. She admitted that she really wanted her mother to be a superhero in order to only have to save people and spend time with her, rather than working. Samantha promised that she would always make time for Ruby whenever her daughter needs her.
Ruby had a soccer game, which her mother attended and cheered her on from the sidelines. Ruby successfully scored a goal and excitedly asked her mother if she had seen it. Samantha, who was on the phone at the time, lied that she did and proudly told Ruby she did a great job. Ruby's team won the match and Sam took them for ice cream to celebrate.
The next day at L-Corp, Ruby was doing her homework on the floor of her mother's office. After finishing, she asked Samantha if they could work on her song for a school recital. Sam asked about Ruby's French extra credit project, to which Ruby spoke in French, having completed that as well. Sam promised to help her with the song later, being too preoccupied with work, and suggested that her daughter start her research paper. A man then entered the room and informed Sam of a problem with an L-Corp merger, which she had to handle. Ruby watched her mother leave, disappointed.
Ruby spent the evening working on her research paper until falling asleep on the couch. Later that night, Samantha returned to her office and tucked Ruby in using her jacket, upset over breaking her promise to her daughter. Sam's boss and friend, Lena Luthor, assured her that showing Ruby how the former can fix issues at work will help the latter understand the importance of her mother's job and learn to be "a badass". What ultimately matters is at the end of the day, Ruby knows Sam loves her.
A few days later at her school's autumn recital, Ruby was delighted to see her mother in the audience. She sang a rendition of "Pure Imagination" while Samantha, Lena, Alex, and Kara Danvers proudly watched, the latter three becoming Ruby's new "cool aunts".
Later that night, Ruby entered the bathroom and found her mother curled up on the floor in fear. Startled, Ruby worriedly called out to her, causing Samantha to snap out of her trance.
Sometime later as Samantha dropped her off at school, Ruby was troubled about the incident in the bathroom, but Sam assured her nothing was wrong. At school, Ruby was greeted by her friend, Luke, who asked if she finished her math homework last night and nervously revealed that he couldn't get through it. Ruby offered to help Luke since there was time before the bell rang, and he gratefully agreed. Suddenly, Luke collapsed on the ground in front of her, seizing. Ruby shouted to her mother for help, and Sam quickly ran over while calling 911. Ruby assured Luke he would be okay, terrified for her friend.
Later that day as Samantha and Lena were talking in the kitchen, Ruby was seen bringing pillows and blankets downstairs to make a bed for Lena so the latter could sleep over. She then stayed at a friend's house for the night.
The next night as Ruby was tucked into bed, she asked about Luke's condition. Samantha assured her he would recover thanks to the cure synthesized by L-Corp, to which Ruby happily complimented her mother's friends. Before going to sleep, Ruby found an odd hole in her mother's shirt.
One evening in December as Samantha prepared dinner, Ruby noticed her mother lost in thought but chose not to dwell on it as she set the table. After finishing, Ruby asked if she could watch a movie after dinner if she finished all of her homework. However, Sam abruptly claimed she had to go back to work and Ruby would have dinner at her friend Tess' house that night. Ruby protested, but Sam brusquely stated that it wasn't up for debate. Slightly hurt, Ruby obeyed and left for Tess'.
The next day, Samantha planned to go on a trip. She told Ruby that Mrs. Queller would arrive soon and left a check for takeout, since Ruby hated her babysitter's cooking. Growing uneasy, Ruby wondered where her mother was going and why she couldn't come with her. Sitting Ruby down, Sam apologized for yelling at her yesterday and explained that she needed to take this trip to gain some answers regarding a secret she recently discovered about herself. Sam then asked to hold her daughter's hand. Ruby felt her mother's pulse, to which Sam proclaimed Ruby is her heart, and everything she was doing was for her daughter. Sam bid Ruby farewell and promised to explain everything once she returned.
The next morning, Ruby heard her mother having a nightmare and rushed to Samantha's room to check on her. Ruby wondered why her mother didn't wake her up after returning from her trip. However, Sam didn't remember going anywhere, much to Ruby's confusion. Ruby insisted that her mother had been gone for the entire day yesterday, claiming she was getting answers to an exciting discovery. Taken aback, Sam brushed off Ruby's story as the former dealing with stress as she hugged her daughter. Upon realizing it was 11 in the morning, Sam and Ruby excitedly ran to the kitchen for chocolate chip and banana pancakes.
Samantha and Ruby attended Kara's Christmas party later that night. Ruby bonded with Alex after the latter revealed that she worked with Supergirl, eagerly asking questions about the superheroine while they sat on the couch. Alex revealed one such adventure involved Supergirl catching her in midair and flying her to safety after the former jumped out of a building during a shootout, much to Ruby's excitement.
On Christmas Eve, Ruby stayed with her mother at L-Corp that evening. Later that night, Ruby entered her mother's office wanting to go out for dinner, as she was hungry and had already eaten all the chips in the kitchen. Samantha sadly explained that she still had work to catch up on and called Mrs. Queller to come pick Ruby up. Upset by this, Ruby snapped at her mother, asking if she would work or sleep through Christmas Day as well and started to leave. However, Sam called her back into the office, apologizing for the late night. Ruby and Sam reflected on a previous Christmas when they moved to Central City, and how the initial dismal experience was brightened by them having fun together. Sam gave Ruby her Christmas present early, which was a necklace of the Supergirl symbol.
On Christmas Day, Ruby rushed downstairs, excited that it was Christmas morning, and called for her mother. After some searching, Ruby found Samantha in the living room looking out of a window. When Ruby approached her mother and called after her again, Sam turned around quickly.
Two days later, Ruby and her mother had a nerf gun battle at home, which resulted in Samantha accidentally breaking a picture, much to the former's amusement. As Sam cleaned up the mess, Ruby left to go to a movie with her friend, Clara, agreeing to make dinner tonight.
Bonding with Alex Danvers
In January, Ruby, Samantha, and Kara visited Alex, whose leg was injured, to drop off some food, with Ruby presenting a tater tot casserole she made herself. Sam had to go out of town on a business trip and discovered that Mrs. Queller canceled on watching Ruby for the day. Alex then volunteered to look after Ruby, much to the latter's excitement.
After a game of Trivial Pursuit, Ruby and Alex began preparing the lunch the former made when Alex received a text from her ex-fiancée, Maggie Sawyer, who needed Alex to mail her passport to her. Ruby found the passport and lent a sympathetic ear as Alex opened up about her heartbreak over the loss of the future she'd planned to have with Maggie. Empathetic to Alex's struggle with her new reality, Ruby revealed that she is being cyberbullied by a girl from school, Erika Morrison, after refusing to let the latter copy off of her homework. Not allowing this, Alex and Ruby left for Erika's house.
Alex used her F.B.I. credentials to confront Erika, warning her of the consequences of online harassment. Erika immediately backed down, promising she wouldn't do it again and agreeing to apologize to Ruby. Outside, Ruby secretly listened in awe while holding Alex's crutches. As the two left, she semi-jokingly attempted to get Alex to confront another girl who'd pushed her in Kindergarten, but Alex told Ruby not to push it.
They returned to Alex's apartment and packaged the passport to be delivered to Maggie. Alex thanked Ruby for being there for her. That night, Samantha returned to collect Ruby and Alex joked about how she was a "nightmare" of a child. Samantha asked Ruby to wait for her by the elevator while she and Alex talked. Ruby hugged Alex before leaving.
Discovering Samantha's secret
Several weeks later, Ruby was surprised when her mother picked her up from school to go ice skating and wondered what the occasion was. Samantha explained she took the day off and asked if they could play hooky today, which Ruby enthusiastically agreed to. At the ice rink, Ruby and her mother enjoyed themselves and had a race, which the former won. When she turned around, Ruby found that her mother had suddenly disappeared.
Scared and confused, she called Lena, who came to pick her up. Ruby explained what happened and revealed she's been noticing something off with her mother ever since Samantha didn't remember going on a day-long trip on December 23. Ruby was afraid and worried about what this could mean for her mother and was consoled by Lena, who promised to help Samantha. Ruby then stayed the night at Lena's apartment.
A few days later, Samantha (falsely) told Ruby over the phone that she was sick in the hospital and Ruby couldn't visit, as she didn't want her daughter to catch her illness. Sam promised she would get better soon and they exchanged "I love you's". Ruby was then placed at Lex Luthor's mansion with Mrs. Queller and cut off from communication with the outside world, though she saw the Pestilence outbreak on the news and believed that her mother came to be a victim of it based on her last phone call.
Several weeks later when Alex came to stay with her at the mansion, Ruby was ecstatic to see her and anxiously asked about her mom. Alex kept dodging the question, vaguely responding that Samantha was still sick, which Ruby easily saw through. Suspicious, she secretly used Alex's phone to try and call her mother, who didn't answer. Ruby left a voicemail expressing her worry, which Reign heard.
When Reign arrived at the mansion, Alex and Ruby rushed to the basement, where Ruby was instructed to stay hidden. Ruby watched as Alex, Supergirl, and Mon-El battled the Worldkiller. Reign eventually incapacitated the heroes as her mask was knocked off. Ruby grabbed a Kryptonite gun, wanting to help, when she saw Reign's face and realized the Worldkiller was her mother, much to her horror. Ruby was frozen in disbelief as Supergirl attempted to reason with Reign that she couldn't kill the young girl, who has not committed a sin. After Mon-El subdued Reign with Kryptonite bullets, Ruby broke down in tears as Alex comforted her.
Samantha was placed at the D.E.O. until a cure could be found, so Ruby was taken in by Alex. Still reeling from the truth, a heartbroken Ruby was upset with Alex for not telling the truth about her mother's problem. Alex apologized and promised to Ruby that she will be honest with her from now on and always protect her.
Ruby is a cheerful, friendly, outgoing, optimistic girl with a love of adventure. She is able to make the most out of seemingly negative situations, as shown when she ended up enjoying an unconventional Christmas spent on the road with her mother. Ruby deeply adores her mother, Samantha, whom she enjoys spending time with. Ruby looks up to her mother and yearns to make her proud, as shown when she excitedly asked if Samantha saw a goal she scored at her soccer game and asked her mother to watch her practice her song for a school recital. Ruby is a huge fan of Supergirl, being fascinated with the superheroine.
Ruby can be naïve, insensitive and even selfish when upset or if things don't go her way. For example, she grew frustrated with her mother's growing responsibilities at work, which cut into their daily lifestyle, even lashing out when Samantha was unable to go out for dinner with her on Christmas Eve due to this. When Ruby believed her mother had superpowers, she hoped this meant Samantha could spend more time with her and not work. She went as far as to walk straight into the path of an out-of-control wrecking ball to prove this, which would have seriously injured or even killed herself and her mother had it not been for the intervention of Supergirl.
However, once Samantha reassured Ruby that she will always be the former's first priority, Ruby began to grow out of this thinking and started to understand the importance of her mother's job, even supporting Samantha in her accomplishments. Ruby developed a close relationship with her mother's friends Lena, Kara and Alex, who became her "cool aunts". She is especially fond of Alex, whom she looks up to as one of the toughest people she knows, with Alex practically becoming a second mother to her.
Ruby is very intelligent and observant; she was able to sense something was off with her mother when Samantha kept forgetting things and blacking out, despite the latter's attempt to hide this from her. She was also able to tell that Alex was lying about her mother's condition. When Samantha was revealed to be the Worldkiller Reign, Ruby was horrified and devastated by this revelation. She slipped into a depression for days, trying to cope with the feeling that her mother may be gone. Ultimately though, Ruby's faith was stronger than her fear as she trusted Lena, Alex, and Supergirl to help her mother. She also believed in her mother's determination when the latter went to combat Reign in the Dark Valley.
Ruby is shown to be mature, reasonable, kind and empathetic; she listened to and comforted Alex as the latter expressed her heartbreak over her breakup with Maggie and even assured Alex she is always there if she needs to talk. Also, Ruby didn't hold her mother's Worldkiller persona against her, understanding that Samantha was not in control and that Reign is a completely separate person. Thus, once Samantha was cured, Ruby happily welcomed her mother with open arms.
- Bilingual: Ruby is capable of fluently speaking English and some French.
- Cooking: Ruby has proficient skill in cooking, having made dinner for her family at least once. She also personally prepared a tater tot hot-dish for Alex Danvers.
- Singing: Ruby is a competent singer and was able to sing a solo in front of a large group of people during a school recital.
- Soccer: Ruby is a talented soccer player and is a forward on her school's team, noted to be very coordinated and graceful. Ruby later became the sweeper keeper on her new school's soccer team.
- Ruby loves ice cream and, like her mother, pancakes.
- Though never explicitly addressed, Ruby is technically a human-Kryptonian hybrid, though doesn't seem to have inherited her mother's powers. This is presumably due to Samantha's powers being magically augmented and part of her separate persona; Reign.