- "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 a Kryptonian hologram, carrying Ruby also delayed her 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 spent Christmas in a truck stop motel at Route 34. They 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 called it her best Christmas since she got to spend it with her mom.
The unveiling and her mother's powers
Ruby and her mother went to the Supergirl statue unveiling, where Ruby bumped into Alex Danvers as she rushed to the front of the crowd. Samantha asked her to properly apologize and she did. Alex accepted and Ruby ran off, excited to see the statue. However, there was an attack at the unveiling, and a metal bar fell on top of Ruby. Ruby screamed for help, and Samantha, frantic and desperate to save her daughter, was able to lift the bar off, putting it down to a rush of adrenaline.
A week later, her mother cooked the two of them breakfast, before driving Ruby to school. Samantha reminded Ruby Mrs. Queller would pick her up, since it was the former's first day at her new job. Partway through the day, Ruby claimed to another student, Stephanie Harrison, that her mother had superpowers, but was called a liar. She then punched Stephanie in the face and was sent to the principal's office. Samantha came to pick her up, disappointed and annoyed that she had to leave work early on her first day. Back at home, Samantha and Ruby discussed what happened. Sam continued to insist she didn't have powers, much to Ruby's frustration.
Ruby snuck out and went to a café for pizza and ignored 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. She then walked straight into the crossfire, hoping that her mother would save her with superpowers. Her mother arrived and hugged Ruby, but a wrecking ball broke off from a truck and plummeted towards them. 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, Ruby and Samantha talked about what happened and Ruby accepted her mother didn't have powers. She admitted that she wanted her mother to be a superhero in order to only have to save people and spend time with her, rather than working. Sam promised that she'd always make time for Ruby.
Ruby had a soccer game, which her mother attended and cheered her on from the sidelines. Ruby scored a goal and excitedly asked her mom if she had seen it. Samantha, who was on the phone at the time, lied that she did and proudly told her 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 her mom if they could work on her song. Samantha asked about Ruby's French extra credit project and Ruby spoke in French, having completed that as well. Sam was too busy but she promised to work on it later. A man then entered the room and informed Sam of a problem with the merger, which she had to handle. Ruby watched her mother leave, disappointed and upset. Later that night, Samantha returned to her office to find Ruby asleep on the couch and placed her jacket over her daughter, sad that she'd broken her promise. Sam's boss and friend, Lena Luthor, assured her that showing Ruby how the former can fix issues at work will help her understand the importance of her job and learn to be a badass. Plus, Ruby knows her mother loves her.
A few days later at her school recital, Ruby sang "Pure Imagination" while her mother, Lena, Kara Danvers and Alex proudly watched.
That night, Ruby entered the bathroom and found her mom curled up on the floor in fear. Concerned, Ruby and asked if she was okay and Samantha snapped out of it.Later as Samantha dropped her off school, Ruby asked her what happened that night in the bathroom. Samantha stated that it was just a bad dream, but Ruby retorted that she was awake. Sam assured her that it was a migraine and told her it was time to get out of the car. Ruby was greeted by her friend, Luke, who asked her if she finished her math homework last night and nervously stated that he couldn't get through it. Ruby offered to help him since there was time before the bell rang, and he gratefully agreed. Seconds later, Luke collapsed on the ground, seizing. Ruby shouted for her mother for help, and Sam quickly ran over while calling 911. Ruby repeated to Luke that he would be okay, scared for her friend.
When Samantha and Lena were talking in the kitchen, Ruby was seen bringing pillows and blankets downstairs to make a bed for Lena on the couch. She then stayed at a friend's house that night. Later on, Samantha tucked Ruby into bed and confirmed that Luke will recover. Ruby pointed out a hole in her mother's shirt, which Sam found weird. They then said goodnight to each other.
One evening in December as Samantha prepared dinner, Ruby asked her mother if she was okay, as she was acting strangely. Sam assured her that she was fine, and told her to set the table since dinner would be ready soon. Ruby did as her mother asked, and then 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's house that night. Ruby was upset by this, but Sam snapped at her and told her that it wasn't up for debate. Ruby, slightly hurt, left for Tess's.
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. Ruby was concerned and wondered why she couldn't go with her mother. Sam explained that she had to do this on her own and asked to hold her daughter's hand. Ruby felt her mother's pulse and Sam stated that Ruby is her heart, and everything she was doing was for her. Sam bid Ruby farewell and promised her that she would explain everything when she returned.
The next morning, Ruby heard her mother having a nightmare and went into Samantha's room to check on her. Ruby asked why her mother didn't wake her up when she returned from her trip. However, Sam didn’t remember going anywhere, much to Ruby’s confusion. Upon realizing it was 11 in the morning, Sam happily declared, "it's pancake o'clock". She 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, asking her questions about the superheroine while they sat on the couch.The next night on Christmas Eve at L-Corp, 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. Sam sadly explained that she had work to catch up on and called Mrs. Queller come to pick Ruby up. Angry at this, Ruby snapped at her mother, asking if she would work or sleep through Christmas and started to leave. However, Sam called her back into the office and apologized for the late night. She and Ruby reflected on a previous Christmas when they moved to Central City. 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. Ruby found Sam looking out of the window. As she called after her, Samantha turned around quickly. Two days later, Ruby is seemingly hiding from her mother until they start attacking each other with nerf guns, which results in Samantha accidentally breaking a picture. As Sam cleans up the mess, Ruby leaves to go to a movie with her friend, Clara.
Bonding with Alex DanversRuby, Samantha and Kara visited Alex, who's leg was in a cast, and dropped off some food. Sam had to go out of town on a work trip and discovered that Mrs. Queller cancelled on watching Ruby for the day, but Alex volunteered to look after Ruby. Ruby and Alex played Trivial Pursuit and as they prepared for lunch, Alex received a text from her Maggie Sawyer, her ex-fiancée, 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. Ruby then revealed that she is being cyber bullied by a girl from school, Erika Morrison, after refusing to let the latter copy off her homework. Not allowing this, Alex and Ruby left for the Erika's house. Alex used her FBI alias and confronted Erika, warning her of the consequences of online harassment. Erika immediately apologized and promised she wouldn't do it again while Ruby secretly listened in awe. They returned to Alex's apartment and packaged the passport to be delivered to Maggie. Alex thanked Ruby for being there for her. Samantha returned and thanked Alex for looking after Ruby, in which Alex joked about how Ruby was a nightmare of a child. Samantha asks Ruby to wait for her by the elevator and Ruby hugged Alex before leaving.
Discovering that Samantha is Reign
Several weeks later, Ruby was surprised when her mother picked her up from school to go ice skating and asked if something was wrong. Samantha explained she took the day off and asked if they could play hooky today. Ruby enthusiastically agreed. At the ice rink, Ruby and her mother enjoyed themselves and had a race, which Ruby won. When she turned around, Ruby found that her mother had 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 she didn't remember going on a day-long trip on December 23. Ruby is afraid and worried about what this could mean and was consoled by Lena, who promised to help Samantha. Ruby 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 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 mom came to be a victim of it based on her last phone call. 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 Reign. 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. She realized the Worldkiller was her mother, much to her horror. Ruby was frozen in disbelief as Supergirl attempted to reason with Reign that she can't kill the former, 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.
- Athleticism: Ruby is very coordinated and graceful. She is a talented soccer player and is a forward on her school's team. Ruby is also good at swimming and ice skating.
- Bilingual: Ruby is capable of fluently speaking English and some French.
- Cooking: Ruby has proficient skill in cooking.
- Singing: Ruby is a competent singer and was able to sing a solo in front of a large group of people during a school play.