Pre-Crisis Her real name is Gayle Marsh. At the age of twelve, she developed psychic powers, primarily psychokinesis. After her parents died, she was raised by the scientist David Pendergast who was preparing to fight a new menace called "the Decay". In college, she took the alias of Psi and fought Supergirl several times, thinking that Supergirl was the Decay. The truth was that David Pendergast was an extension of her own fears. Realizing that the Decay was David and herself, she put a stop to Pendergast and herself. Post-Crisis Psi's first appearance in the Post Crisis DC Universe was with the Suicide Squad. She had no memory of her real name or history, as an unknown event "has nearly shattered her psyche". She joined in order to gain help from the Suicide Squad in restoring her lost memory and accompanied Rick Flag and a similarly untested team for a mission in Central America, but she was killed by the Rocket Red Brigade. As she lay dying, she remembers her real name, Gayle Marsh, as well as her mother and father. Her allies, Mister 104, the Thinker and the Weasel are also killed on the mission. During the events of Blackest Night, Psi's corpse is reanimated as a member of the Black Lantern Corps alongside several other fallen Suicide Squad members. Psi is apparently destroyed by the Manhunter's self-destruct mechanism unleashing an explosion of Green Lantern energy that eradicates the Black Lanterns. The New 52 In September 2011, The New 52 rebooted DC's continuity. Psi is reintroduced as a prisoner in "The Circus", the Detroit station for A.R.G.U.S. operations. Steve Trevor and Killer Frost visit her cell to see if she can disrupt the Firestorm Matrix in order to free the imprisoned Justice Leagues. When Psi touches him however, Trevor is flooded with images, which he realizes connects everything he already knew, based on the clue Madame Xanadu told him, and tells him how to save the Justice League. One of the visions that Psi showed Steve Trevor was that Wonder Woman's lasso is in the possession of Cheetah.
Psi appears in Supergirl, portrayed by Yael Grobglas. This version was "a law-abiding citizen of Skokie, Illinois" until she "snapped" and began robbing banks. A separate incarnation of Psi appears in the tie-in digital comic Adventures of Supergirl. This version is a Kryptonian psychic who worked in the maximum security prison Fort Rozz as a "dream mistress", controlling the prisoners' dreams to secure their mental health, before losing her physical form when the prison crashed.