Caitlin Snow (Earth-1: Pre-Crisis)

"When I was a resident, fresh out of med school, one of the first things they taught me is that sometimes, you lose a patient. That death is a part of life."

- Caitlin Snow

Dr. Caitlin Snow, M.D. is a biochemist at S.T.A.R. Labs who has dissociative identity disorder after her father attempted to cure her amyotrophic lateral sclerosis (ALS). The alter, Killer Frost, surfaced years later after the Flashpoint. Snow is also the daughter of Carla Tannhauser and Thomas Snow.

When Snow first discovered her alter, Killer Frost took control of her body for criminal activities before they made peace with each other. Snow soon returned to Team Flash and was eventually split from Frost after an injury caused by Eva McCulloch's Mirror Gauntlet.

S.T.A.R. Labs
Prior to 2013, Snow and "Harrison Wells" was experimenting on Grodd, a gorilla. She then grew fond of him and took care of him. Snow then became the only person Grodd trusts and was considered a good person by him.

Killer Frost
At some point prior to 2019, Snow's split personality was created by her father and became a villain known as Killer Frost. Later, she sought help from her mother and was unable to cure herself. However, as time passes, she realised that Killer Frost is not truly a villain and worked with her to reform and become a member of Team Flash.

Years later, Snow fought his father's split personality, Icicle.

Rebranding as Frost
In 2019, Snow rebranded Killer Frost as Frost and allowed her to take over her body in order to finally live a life. Additionally, as Frost has been in the "passenger seat" of Snow's mind for years, she retains Snow's knowledge on biology and chemistry.

Crisis on Infinite Earths
In January 2020, Nash Wells was found unconscious in his own worksite. He was then brought to S.T.A.R. Labs and was treated by Snow. She was then approached by J'onn J'onzz, who gave her the memories of her Pre-Crisis counterpart. She then realised the destruction of the Multiverse was Nash's fault.

After the battle, Snow takes over her body once more and attended the moment of silence with Barry.

When Wells' body was taken over by Eobard Thawne, Snow was able to determine that the mind of Nash was also tangled with his Pre-Crisis counterparts'.

Doctor's Orders
When Allen started losing his speed, Snow and Ramon was able to create a Speed Gauge for Allen to monitor his speed. Despite the device, Allen insisted on using his speed to fight crime instead of letting Frost be on the field. Snow then briefly transformed into Frost and ordered Allen to stay, who did not listen and made Snow injured during the fight.

Leave of Absence
"Maybe instead of focusing on what you've lost, you should try remembering what you'll never lose. The reason you've beat Zoom, Godspeed, Thawne? It's because speed isn't what drives you. It's love. That's your true force, and there is nothing artificial about that. So as long as you stay true to yourself, you will always find a way to beat the bad guys. And gals."

- Snow to Barry Allen

Due to Snow's injuries during the fight against Kimiyo Hoshi, she attempted to use "ice healing" to speed up the process. However, it backfired and caused her to fall into a coma, until her teammates visits her at her apartment. After Frost agrees to seek help from Snow's mother, she left to the Arctic for tests and recovering.

Return
Four weeks later, Snow and Frost arrives back in Central City, fully recovered and ready to return to the field.

After the Invasion of Central City, Snow bid farewell to Ralph Dibny, who suffered from injuries after being exposed to high temperature.

Split from Frost
A week after the Invasion, Snow and Frost suffered from headaches and went for a sleep, only to wake up in separate bodies. They then approached Cisco Ramon and surprised him with their sudden change. Ramon later brought them to the Cortex and surprised Allen and West-Allen.

They then went to the lounge and discussed the prior events to the split. Allen then sped off to fight Psych and later Frost assisted the treatment of his injury. Ramon then started fixing the Quantum Splicer for the merge and the device was damaged by Frost. Snow then confronted her and Frost told her that she do not want to merge as she could finally live her own life without being inside Snow's body.

Hours later, Snow diagnosed the trio with panic attacks after fighting Psych and placed in their greatest fears. Frost was alone in the Speed Lab until Snow looked for her. While Frost fixes the Quantum Splicer and tell her about her own fears, Snow offered Frost to sleep in an extra room in her apartment and considered her a sister.

Time Pocket
In her apartment, Snow started to realize that Frost is becoming a separate person and diverged from herself. Snow then returned to S.T.A.R. Labs and was affected by the Time Pocket created by Deon Owens, with her appearance becoming that of 1950s. Luckily, it was reversed when Ramon and Runk, both being in 1998, convinced Owens to stop his actions. Snow then once again attended a team meeting where Ramon names the Forces of Nature.

The People v. Killer Frost
When Kristen Kramer arrived in Central City in order to arrest Frost, the Meta Task Force arrested Snow under an anonymous tip of Frost's residence. Horton served as Snow's attorney while Snow convinced Frost not to break her out of the precinct. The call then allowed Frost to understand who the imposter of her actions was.

Frost was then allowed to discuss her next move with Team Flash, with the team assisting her legal battle. Snow was then present at the trial, where she attempted to sabotage the Metahuman Cure in order to prevent Frost's power removal punishment. Snow, Cisco and Garcia then went to the precinct and created a distraction for Garcia to deploy the Inertial Oximeter. However, Garcia was discovered by Kramer and Snow took charge, sabotaging the cure by herself. Unfortunately, Kramer accused Frost of the sabotage and Snow defended her "sister", telling the court that she did it. Despite all the efforts to protect Frost, she insisted that she should be sent to prison for life with no possibility of parole. Snow then bid farewell to her sister as she gets taken to Iron Heights.

Days later, Snow monitored an unconscious Alexa Rivera, who she discovered that her powers briefly activated when there were tremors. Allen and West-Allen then resurrected her with a small fraction of Strength Force energy.

After the "Unforgiving Storm" between the Forces of Nature, Snow was greeted by Frost in her own apartment and found out that Frost was responsible for the arrest of countless escapees of Iron Heights.

Goodbye Cisco
One day morning, Snow, Allen and West-Allen were called to the lounge as Ramon and Hawang told them about their leave from Central City. Despite her sadness over her best friend leaving, Snow did not show any sign of sadness and requested Ramon's security badge. He was disappointed over the team ignoring his important decision and later saw Snow talking to Allen on the second Rainbow Raider. Ramon then proposed a final mission. Snow then monitored their first confrontation with Rainbow Raider, where Ramon was hypnotized. Ramon and Snow then guided Allen to Rainbow Raider's location. However, Ramon's extensive joy affected Allen's sight and Snow attempted to stop him. Unfortunately, it was too late and Allen was affected as well. Snow then saw the two being extensively joyful, with no means of fixing them until Runk arrived and neutralized the effects.

Snow and Allen then told Ramon that they acted courageous to prevent their last day from being pitiful. They then worked together to defeat Rainbow Raider, and later planned a surprise party. Ramon then gave Snow his shirt on his first day, that says "Keep Calm and Han Shot First". The original members of the team soon sang Poker Face, the alleged favourite song of Barry Allen as shown in his Facebook profile page.

Powers

 * Renerative Healing Factor/Longevity: After Snow was transformed by Deathstorm, her cells fell into a continuous state of regenesis and did not age according to normal human biology.

Former Powers

 * Transformation: Snow is able to transform into Frost at will until their separation.
 * Cryogenic Physiology: In an attempt to cure her amyotrophic lateral sclerosis (ALS), Thomas Snow experimented on both himself and Snow, making them both developing dissociative identity disorder and a cryogenic physiology when the alter fronts. However, Frost was later split from the body of Snow when the effects of Eva McCulloch's Mirror Gauntlet spliced their bodies.
 * Thermokinetic Cryokinesis: By drawing heat, Frost is able to freeze objects within a radius without even touching them.
 * Accelerated Healing: Also known as "ice healing", Frost can use her cryokinesis to speed up the healing process.
 * Cryokinetic Breath: Frost is able to breathe out cold air and freeze objects.
 * Cryokinetic Blasts: Frost has the ability to create cold blasts of ice from her bare hands.
 * Cryokinetic Constructs: With precise concentration, Frost can create objects with ice and use them as weapons, most commonly daggers for hand-to-hand combat.
 * Superhuman Durability: Despite being hit with a bullet, Frost only suffers from minor injuries.

Former Powers

 * Powers via Velocity X: Frost injected herself with Velocity X as a countermeasure against The Flash.
 * Superhuman Durability: Frost is able to survive a fall from a tall skyscraper in high velocity with little injuries.
 * Superhuman Speed: After injecting herself with Velocity X, Frost gains superhuman speed.
 * Superhuman Stamina: Despite running long distances, Frost is able to continue moving until the Velocity X wears off.

Abilities

 * Biochemistry: Snow attended medical school and has the rank of doctor.
 * Medical Knowledge: Snow has proven to be an expert on treating patients.

Former Equipment

 * Frost Suit: As Frost, Snow wears a navy leather suit with a snowflake emblem on the chest as well as a blue jacket. As they are no longer in the same body, Snow does not wear the suit anymore.