As a married couple, both Leslie and Frank Dean were exiled convicts from the planet of Majesdane. As aliens, they had the natural ability to absorb solar energy. This solar absorption gave them both the ability to fly, fire energy beams, create shields and bonds. They were also bursting with colourful light, appearing to be humanoids made of light, energy and colour.
Together they settled in Hollywood, and through the use of a metallic substance they could repress their natural alien abilities in order to live among the human population. By purchasing a property without any surrounding buildings or neighbours, they were free to use their powers in private without being observed. Both Leslie and Frank created a public persona of themselves which was extremely clean and caring. They were popular actors on General Hospital who were also vegan and preferred to listen to music from the 60's, including The Beatles. This false persona was so strong and believable that nearly twenty years later their own daughter would refuse to believe that they were capable of murder, stating that they don't even eat meat.
Together, Leslie and Frank were off set reading through a script when they were summoned by The Gibborim. They were instantly teleported to the underwater Vivarium where 10 humans had also been gathered. Tina Minoru recognised them from General Hospital, but Geoffrey Wilder threatened to shoot them if it was part of some publicity stunt. This prompted Leslie to reveal her alien powers in self-defence. Victor Stein wanted to know how she created a concussive light blast, which Stacey Yorkes dismissed as mutant powers. Leslie, offended by the Yorkes' mistaken identity, stated that neither she nor Frank were freaks. The foray continued to descend until The Gibborim appeared before them.
When The Gibborim made the offer of 25 years of unlimited power over Los Angeles and the possibility of immortality, they classed Leslie & Frank Dean as "The Colonists". They agreed to have their powers enhanced, and the chance that they would be among the six offered immortality after The Gibborim destroy the Earth. As such, they became founding members of The Pride. Neither Leslie or Frank bothered to deceive the other Pride members with their public persona, and were comfortable enough around them to show their true cruel characteristics.
After Victor and Janet Stein announced that they were pregnant and intended to give their chance of immortality to their child, the Deans also hoped to have a family. Soon they had a baby girl, Karolina Dean, who had inherited her parent's solar based alien powers. In order for Karolina to grow up as a normal human child, they had a medical bracelet created from the same metallic substance that suppressed their own alien abilities, and it was agreed that they would not reveal anything about her true nature of The Pride until her 18th birthday.
In the off-chance that something should happen to them before Karolina's 18th birthday, the Deans drafted a Last Will and Testament. The last page of which contained a symbol which indicated the removal of her medical bracelet. The will was found by Chase Stein on the night that the Runaways observed The Pride murder a young prostitute in the Ritual of Blood. Karolina, who had not seen the Ritual, still refused to believe her parents were capable of murder and ripped the bracelet off in a fit of anger and inadvertently unleashed her alien powers.
Karolina believed her parents had flown to New York for the reading of a Broadway play, but they were actually brokering an intergalactic arms deal. Therefore Leslie and Frank were unable to prevent Karolina from discovering her powers. When the other members of The Pride called them to inform them of events, it was Leslie who took the shuttlecraft back from New York to Los Angeles. Leslie dismissed the possibility of Karolina being a potential threat, having raised her to be a friendly and spineless child.
Leslie later confronted Karolina behind the Hayes' property. Using her alien powers to bind Chase, she confirmed to her daughter that they were aliens, and the nature of their abilities. Although she claimed that all she wanted to do was give her daughter a normal upbringing in Hollywood, Leslie was knocked unconscious when Karolina punched her with the medical bracelet. Leslie later joins the fight by blasting a hole in Molly Hayes' bedroom wall. She revealed her true condescending nature and threatened to crush Gertrude Yorkes. However, Leslie had arrived to the fight after the revelation of Molly's latent mutant powers, and was therefore caught off guard by the little girl's super strength. Leslie was shoved back out of the hole she had blasted in the wall, and landed unconscious in the Hayes' swimming pool.
While she was floating face down in the pool, Alex Wilder removed the decoder ring from Leslie's hand, which he would go on to decode The Abstract with. However, as soon as she regained consciousness she grabbed Nico Minoru and threatened to kill her. While screaming threats she was knocked unconscious yet again, this time by Alex wielding the Staff of One as a club.
Betrayal & Death
A year before the Runaways ran away from home, both Leslie and Frank Dean had begun to conspire with Alice and Gene Hayes. The Hayes were mutants, classed as "Outcasts" by The Gibborim. Set aside from the rest of humanity, they did not consider themselves to be human and therefore bonded with the Deans. Together, the four adults realised that instead of just giving their children the chance to become immortal, they could join them.
The pact with The Gibborim meant that six out of the twelve members of The Pride would become immortal. Together the Deans and the Hayes realised that if they were to remove the remaining eight members of The Pride, then they could become immortal along with their children, Karolina and Molly. However, realising that the future of The Pride was already recorded in The Abstract they set about decoding their own copies. After they had identified which pages revealed their treacherous plot, they silently broke into the houses of the other Pride members to remove those pages from the other four copies of The Abstract.
While breaking into the Wilder residence, they were silently observed by Alex. Discovering their scheme to murder his parents, Alex began to form a plan of his own. Like the plan of the Deans and Hayes, Alex's plan would guarantee immortality for his family, and for the Minoru family, as he had fallen in love with Nico. However, Alex's plan begun to fail when Nico rejected him. The Gibborim were angered when their human soul was released before they could devour it, and turned their wrath on all The Pride and the Runaways. As a last act of familial loyalty, the Pride used their powers to hold The Gibborim back while their children escaped.
Leslie Dean has not been seen since the Vivarium was destroyed in an underwater explosion. Both she and her husband have been presumed dead.