- "Did you know that rubies are one of the toughest gemstones?"
"Only diamonds are tougher."
- —Alex Danvers and Ruby Arias[src]
In her teens, Ruby's mother Samantha, who was unknowingly the human alter ego of the Kryptonian wordkiller "Reign", became pregnant with her to a human father. She was kicked out of the house by her adoptive mother, Patricia Arias as a result. According to a Kryptonian hologram, carrying Ruby also delayed her mother's development into Reign.
At one point, Ruby moved with her mother to Central City, where Samantha had received a new job and was mad that she had to leave her friends 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 that her mother had superpowers, but being called a liar, she punched the girl in the face, causing her mother to be called to the school. Back at home, Samantha and Ruby discussed what happened. Ruby grew frustrated that her mother wouldn't admit to having powers.
Ruby snuck out and went to a café where she ordered two slices of pizza and a drink. While there, Psi launched an attack outside, which caused Ruby to text her mother back with her address and an SOS message. She then walked straight into the street, where the majority of the fight was. Her mother arrived and hugged Ruby, but a wrecking ball almost crushed them. Before they could be crushed, Supergirl intervened and caught the wrecking ball and moved it aside.
Following the ordeal, the pair recovered in the back of an ambulance, and the two talked about what had just happened. 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 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. Samantha promised that she'd always make time for Ruby.
Ruby had a soccer game later that week 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 was mentioned by a woman who wanted to recruit both Ruby and Sam to a cult group and believed them both to be "special". That night, when Alex asked if Ruby's father was still in the picture, Sam said it was just the two of them.
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. Samantha was too busy but she promised to work on it later. This upset Ruby, and when a man entered the room and informed Samantha of a problem with the merger, she had to handle it. 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. Lena assured Sam that showing Ruby how the latter can fix issues at work will help Ruby to be a badass. Plus, Ruby knows her mother loves her. Later at her school recital, Ruby sang "Pure Imagination" while her mother, Lena Luthor, Kara Danvers and Alex proudly watched.
Ruby entered the bathroom that night and found her mom curled up on the bathroom floor in fear. Concerned, Ruby and asked if she was okay.
Later, Ruby's mom dropped her off school. Ruby asked her mother 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 that 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 stopped moving and collapsed on the ground, seizing. Ruby shouted for her mother for help, and Sam quickly ran over to help while calling 911. Ruby repeated to Luke that he would be okay, scared for her friend.
When Sam 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, as Sam tucked her into bed, Ruby asked her mom if Luke was going to be okay, and Sam confirmed that he will. Ruby told her mom that she liked her friends, and Sam told her that she liked them too - but liked her more. Ruby pointed out a hole in her mother's shirt, which Sam found weird. They then said goodnight to each other.
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. Sam, who was surprised by her newfound ability to withstand temperature changes, said that 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.
Later, Sam packed her bags and planned to go on a trip. She told Ruby Mrs. Queller would arrive soon, and left a check for takeout since Ruby hated her babysitter's cooking. Ruby was concerned about her mother and asked if everything was okay, and why she couldn't go with her. Sam stated 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 said that it was her - 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.
Ruby was awakened the next morning by her mother, who had a nightmare. Ruby went into her mother's room to check on her and asked why she didn't wake her up when she returned from her trip. However, Samantha didn’t remember going anywhere, much to Ruby’s confusion. Upon realizing it was 11 in the morning, Sam declared "it's pancake o'clock". She and Ruby excitedly ran to the kitchen to make chocolate chip and banana pancakes.
The next night on Christmas Eve at L-Corp, Ruby entered her mother's office and asked her if it was time to go for dinner as she was hungry and had eaten all the chips at the kitchen. Sam sadly explained that she had work to catch up on and had 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 Danvers
Ruby, Samantha and Kara visited Alex who's leg is in a cast after her encounter with Reign. Samantha, who had to go out of town on a work trip, 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, 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 F.B.I. 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 as she held Alex's crutches. They returned to Alex's apartment and placed the passport in an envelope 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 to look after. Samantha asks Ruby to wait for her by the elevator and Ruby said goodbye to Alex.
Discovering that Samantha is Reign
Several weeks later, Ruby was surprised when her mother picked her up form school and asked if something was wrong. Samantha said that 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. Ruby won and turned around, but found her mother gone. Scared and confused, she called Lena, who came to pick her up. Ruby explained that her mother suddenly disappeared and she's been noticing something off with Sam 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. Lena consoled her, promising to help Sam and find out what's wrong. Ruby stayed the night at Lena's apartment.
A few days later, Sam (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. 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 caught Reign's attention due to her super hearing.
When Reign arrived at the mansion, Alex and Ruby rushed to the basement, where Alex instructed Ruby to stay hidden and close her eyes. Ruby watched as Alex, Supergirl and Mon-El battled Reign. Reign eventually incapacitated the heroes as her mask was knocked off. Ruby grabbed the 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 in holding at the D.E.O. to contain her until a cure was found, and Ruby was taken in by Alex. Still reeling from the truth, a heartbroken Ruby was upset with Alex for not being honest 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 an intelligent young girl who is able to figure situations out, such as the fact that she knew her mother had superpowers before Samantha did. She is also a kind-hearted girl who has an optimistic view on things, and is able to make the best out of otherwise negative situations. This can be seen when she didn't get upset after her and her mother were attacked by the villain Psi, and when she enjoyed a Christmas spent on the road. However, Ruby can sometimes be emotional and selfish, like when she was angered by her mother claiming that she didn't have superpowers, and put herself in direct harm to prove herself right. She also snapped at her mother because she slept in late and wasn't going to spend Christmas Eve night with her, as she had to work.
- 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.
- Soccer: Ruby is a good soccer player, and is a forward on her school's team.
- Bilingual: Ruby is fluent in English and some French.
- Like her mother, Ruby loves pancakes.
- Samantha's biggest fear is losing Ruby.