N'Astirh was a demon that lived in Limbo. He has proven to be a master manipulator that enjoys the corruption of those he chooses as his targets.
Mayor Story Arcs
While Illyana Rasputin was trapped in Limbo, he pretended to help her by defending her against S'ym. All the while, manipulating her to further his own agendas. This eventually led to him and his demons to invade earth. During this time, N'astirh tried to wreck as much havok on earth as he could. He also made a pact with Cameron Hodge, promising him immortality. Besides that, he awoke the dark side of Madelyne Pryor through her dreams, causing her to become the evil Goblyn Queen. Then manipulated her further while posing as her servant. Longshot, one of the few X-Men unaffected by Inferno, was bitten by N'Astirh, corrupting him and causing him to use his luck for selfish purposes, which led to him doubting and second guessing himself afterward.
He messed with Hobgoblin by giving him more power but the demon inside Hobgoblin started taking over his body. this would later lead to the creation of the villain Demogoblin.
N'Astirh was long believed to have been destroyed by Iceman who froze the entire demonically corrupted Empire State Building, while Storm surrounded the ice in a humid heat. Once the ice was shattered by Colossus and Dazzler, N'Astirh orginially thought that they had mistakenly done him a favor because the cold had made his new techno-organic body even more efficient, but he quickly felt the effects of the humidity. Before he could act, Storm furiously unleashed her lightning, overloading his circuits and destroying him.
N'astirh would appear as a boss fighting Spider-Man in Spider-Man / X-Men: Arcade's Revenge.