Uncanny X-Men #239, 240, 241, 242, 243
X-Factor #36, 37, 38, 39
The New Mutants #71, 72, 73

Inferno was a direct result of Illyana's (Magik, The Darkchilde), loss of control over her realm of Limbo. She had inherited the realm many years before when she disposed of it's demon lord, Belasco. She spent years there, while only seconds passed on earth, and entering as a child and returning a teenage girl when her brother, Colossus, pulled her from the portal. Always at odds with Belasco's former henchman, S'ym for the right to rule the demon filled dimension of Limbo, he finally got the better of her one day. Taking her Soulsword into his possession, he let loose the demons onto the earth, and the earth itself began to change as well. Inanimate objects began to take on demonic and twisted life, and even the X-Men did not escape unscathed, becoming more evil in intent and appearance.

They arrived on the scene in pursuit of the Marauders, only to find Sinister, playing his hand in the Inferno. He intended to use his creation, Madelyne Pryor, Jean Grey's clone, to further the chaos which ensued. But she suprised him, displaying the Phoenix power she still held within her, as well as some of her own. She proved the stronger, and went with her own agenda. Joining forces with a demon called N'astirh, she planned to sacrifice her son, Nathan Christopher, to form a permanent bridge between Limbo and Earth. Meanwhile, The New Mutants and Excalibur were fighting their own seperate battles against the demons, and X-Factor came on the scene, meeting up with the X-Men for the first time since their supposed death during the Fall of the Mutants. Not quite believing that these demonic X-Men were the real thing, the two groups fought each other at first, then joined against Madelyne, now the Goblyn Queen. All except for Havok, who joined Madelyne instead, believing her to be the one who was wronged. All sympathy fled when he saw her true nature, however, yet he stood by her nearly to the end.

It was her hatred for Jean Grey that destroyed the Goblyn Queen in the end. Believing that the world was not big enough for the two of them, she attacked Jean psionically, threatening to take her with her into death. Jean survived only by reaccepting the part of herself the Phoenix had stolen years earlier, the part which had given her clone, Madelyne, life. It fled Madelyne as she died, re-entering Jean and making her whole again. The child recovered, the chaos soon died down, though the source of it's end was not yet known to them.

In actuality, Illyana (Magik), had been forced by Rahne to face her childhood self, the innocent girl who had first entered Limbo so many years ago. She decided to renounce her power and thus sealed Limbo, somehow changing time and erasing all that had happened to her in the past several years. In the teenaged Illyana's place was left the little girl that Rahne had found in Limbo. Limbo returned to it's normal state, reclaiming all of the demons it had released, and so, the Earth to returned to normal. S'ym and N'astirh both met terrible fates, and are presumed dead. Illyana, with a second chance at childhood, later developed the Legacy Virus and died. The Soulsword found it's way to Illyana's best friend, Kitty Pryde (Shadowcat), but those are stories for another day.