Zagan was a powerful demon introduced in Tower of Shadows, a horror comic published by early Marvel comics - he is the classical "evil genie" of villain lore and has vast powers allowing him to travel to and from his own Hell-dimension and alter reality as well as grant the wishes of those that summoned him.

Zagan was not a particularly reliable "ally" however as the would-be-warlock known as Brother Alistar learned when he summoned the demon to exact revenge on a world he believed had wronged him, upon being summoned Zagan transported Brother Alistar to Hell and punished the two hippies who had the misfortune of being in the house at the time by turning them into what they feared the most: a "normal" middle-aged couple with a child and blue-collar jobs.

Zagan was never heard of again but could very well still exist somewhere in the more obscure areas of the Marvel Universe, being an immortal demon.