Created by writer Chris Claremont and artist Salvador Larroca, the character first appeared as Regan Wyngarde in X-Treme X-Men #6 (December 2001).

[3] She was originally involved in a plot created by Sebastian Shaw to have his revenge against Sage and gain control of the Sydney underworld.

This plot was created by using Regan's telepathic illusionary powers to assassinate Miles Warbeck, an Australian underworld crime lord known as Viceroy, and framing Gambit over his death.

[5] However, with the assistance of Lifeguard, the daughter of Viceroy, Sage was able to break the illusion and reflect Regan's powers back against her, leaving her in a vegetative state.

It was stated that Regan fell victim to scientists of the Fordyce Clinic who were trying to determine if a person can catch mutation like a disease.

While there the island is attacked by an ancient Shi'ar superweapon known as the Hecatomb, forcing Regan and the rest of the team to fight the psionic horror.

Initially confused by the seemingly invisible nature of their opponents, the X-Men are caught off guard when Regan drops her illusionary cloak to reveal the Marauders.

[10] Along with fellow Marauders Sunfire, Gambit, Prism, Blockbuster, Malice, and Scalphunter, Regan travels to Cooperstown, Alaska to find the baby but instead come across the Purifiers and they come to blows.

[12] When the X-Men, X-Factor, and X-Force arrive on Muir Island, Lady Mastermind attempts to cast an illusion to hide the Marauders.

[3] Later, when the Sisterhood attack the X-Men, Regan takes out Emma Frost by trapping her in an illusion and then leaving her bound and gagged in a dark room, cutting her off from her senses.

[15] When they return to base, the Red Queen orders Regan, Martinique, and Psylocke to stay while she and the other members of the Sisterhood go to Jean Grey's grave.

[20] Regan manages to temporarily escape the team by projecting an illusion of the Avengers who had come to take the time displaced original X-Men.

[22] Following the rebirth of the Marvel Universe, Regan is revealed to be one of the many mutants poisoned by the Terrigen Cloud roaming the Earth's atmosphere.

[23] After her recovery, Lady Mastermind was eventually welcomed to the new mutant island of Krakoa, created by Xavier, Magneto and Moira.

She entered through the teleportation gateway alongside other villainous and fractious mutants, who had been invited to join the nation in order to heal mutantdom and start over as a whole species together.

After Cypher, a member of the scouting party, manages to establish a rapport with the Sidri, Regan is liberated and taken back to Krakoa.

[27] Lady Mastermind possesses the mutant power to project extremely convincing and realistic illusions into the minds of others, the same ability her father had.

She confronted Viceroy with the illusion that he was drowning, and, believing it to be real, he suffocated, despite having no physical injuries and being in a room with sufficient oxygen.

The White Queen found that her cognition was too interrupted to even understand what was happening, much less summon her own psionic abilities to fight back.

In addition, unlike her father, both Regan and her half-sister Martinique have limited telepathic abilities that enable them to read their opponent's mind and make their illusions all the more accurate for it.

Lady Mastermind has a distinct personality, to a point where writer Mike Carey refers to her as an "exuberant, sexy sociopath".

[36] In the future depicted in X-Men: The End, both Martinique and Regan fell prey to Mister Sinister and he turned them to stone.

Thanks to a telepathic nudge from Jean Grey, Wolverine broke free of the illusion and destroyed the statues, ending Regan’s torture.