The succubus daughter of a lesser Chaos Lord and an unidentified mother, Pandemonia terrorized central Europe through the Middle Ages. She feasted on the life forces of her servants and transformed villages into her own version of hell. Her reign of terror was finally ended when a Romani ("Gypsy") sorcerer imprisoned her on Mount Sorcista in what would become the country of Latveria.
When the space-warping mutant terrorist known as Locus teleported herself and X-Force member Skids to Mount Sorcista she broke through the mystical boundaries that held Pandemonia prisoner. The ancient succubus easily overcame the two girls, using her powerful magic to capture them and then imprison them in her dungeon. Etching her mystic symbol onto the Locus' forehead, Pandemonia managed to gain control of the young mutants mind. When Skids tried to escape, the succubus placed a mind-controlling sigil on her forehead as well.
Pandemonia then made Locus teleport the three of them to X-Forces home in San Francisco where she ambushed and took control of Skids teammates: Meltdown, Sunspot, Siryn, and Proudstar. Pandemonia had used her powers to reshape X-Force's warehouse headquarters into a dark Gothic castle and her possessed X-Force were prepared to attack when Cannonball, Moonstar, and Jesse Bedlam returned from an exercise session. Because of status as a former Valkyrie, Dani Moonstar proved immune to Pandemonia's sigil. This unforeseen resistance disrupted the demonic sorceress' focus and Moonstar was able to evade her mind-controlled comrades and escaped with Bedlam and Cannonball.
Desperate to find away to combat Pandemonia's magic, the trio searched through occult bookstores and eventually they were referred to the home of the sorceress Jennifer Kale. Kale was able to gather a remarkable amount of information about Pandemonia in a mystic tome that she referred to as her "handy Demonic Concordance." The Concordence revealed Pandemonia's history and gave Kale Valuable secrets that she would be able to use against the succubus.
Realizing they needed to strike quickly while Pandemonia was still weak from her centuries of isolation, Kale led the trio of young heroes in a head on assault. While Moonstar, Cannonball and Bedlam held off their ensorcelled friends, Kale cast a spell, which revealed Pandemonia's gruesome true appearance and released the possessed mutants from her mind-control spell. With all X-Force behind her, Kale was able to banish Pandemonia, not just to her prison in Mount Sorcista, but to her far more distant Chaos Plane.