Around her late teenage years, Siena Blaze discovered she was a mutant with the power to manipulate the Earth's electromagnetic field. Siena's father was the first person to observe how her abuse of this power could endanger all life on the planet, but Siena was indifferent. Looking for entertainment, Siena aided Wallace Benton in a crime spree through New Mexico that ended with them surrounded by the police. Siena was rescued by Trevor Fitzroy, a mutant from an alternate future of Earth-1191, who was told to find Siena by her future counterpart. Fitzroy slew the policeman and Benton, then recruited Siena into the Upstarts, a team of young hedonistic thrill-seekers gather together by the ominipathic mutant Gamesmaster to kill mutants for sport while they earned "points." Siena was intrigued by the prospect and accepted the invitation.
On her first assignment from the Gamesmaster, Siena attempted to kill the three leaders of the X-Men:Professor Charles Xavier, Cyclops (Scott Summers) and Storm (Ororo Monroe). As the three traveled over Antarctica aboard their Blackbird jet, Siena used her powers for only the third time in her life, generating an electromagnetic blast that downed the Blackbird. However, the three X-Men survived, and, despite Siena's superior power, their well-honed tactics enabled them to defeat her. Overexerted from combat, Siena quickly teleported away to safety. When Mister Sinister requested the Gamesmaster to obtain the DNA of Proteus (Kevin MacTaggert), son of Excalibur's Moira MacTaggert, the Gamesmaster gave the assignment to Siena, telling her that Moira's death would be considered a "point" in their scoring system. Siena attacked an oil drilling operation near Muir Island to distract Excalibur, but the team caught up with her in time to save Moira's life and retrieve the disc containing Proteus' DNA coding. Having again depleted her power, Siena escaped.
Siena participated in the Upstarts' "Younghunt" as the Gamesmaster instructed them to bring live members of the New Mutants and the Hellions. Siena scored five points by capturing Cannonball (Sam Guthrie), Boomer (Tabitha Smith), Daniel Moonstar, Karma (Xi'an Coy Manh) and Empath, although all eventually escaped. While attempting to score points for the capture of Reaper (Pantu Hurageb) of the Reignfire-led Mutant Liberation Front, Siena and Reaper were caught in a tear in the fabric of reality caused by Amber Hunt, a superhuman from Earth-93060 (the "Ultraverse"). Siena and Reaper wounded up in Reality-93060's mystical Godwheel realm, along with fellow Earth-616 resident Juggernaut (Cain Marko), the three reality refugees fell into an uneasy partnership with Amber, Shuriken (Brittany Chien) and Strike (Brandon Tark). The six of them put aside their differences and combined their powers to arrive on Earth-93060 at the exact time of a catastrophe that killed thousands in Manhattan. The six powerful beings were accused of causing the disaster and they never learned if they were truly responsible; bound together as outcast, they dubbed themselves as the Exiles. Siena remained with the team in part because of an attraction to Strike. Juggernaut returned to Earth-616, but the other Exiles remained to clash with the like of Harvest (an agent of the mysterious Tradesmen), Sixx, the tentacle and telepathic creature Moloch and Aladdin agents Rocket and Blast. Finally, the techno-organic being Maxis opened a portal to Earth-616 and Siena, Reaper and the Black Knight (Dane Whitman) returned home.
Siena kept a low profile until she was rounded up by Malcolm Colcord, director of Weapon X, and sent to the Neverland concentration camp with dozens of other mutants and put to death. A short time later the immortal mutant Selene used a modified techno-organic transmode virus to resurrect hundreds of dead mutants, including Siena. Siena was used in an assault upon Utopia, the new headquarters of the X-Men, but supposedly died again when Selene was killed by X-Force.