Vilitch the Curseling
Vilitch the Curseling, also called the Twisted Twin is a mutant Sorcerer of Tzeentch, fused to the body of his twin brother Thomin.
History
Pre-End Times
Vilitch and Thomin were twins, whose births killed their mother. Where Thomin was healthy, strong, and good looking, Vilitch was the opposite, being frail, weak, and ugly. Growing up, Vilitch was forced to do the chores of his dead mother, suffered beatings from Thomin, and was forbidden from using a sword. As they grew up, Thomin became a great warrior, while Vilitch was barely able to get by as the local shamans apprentice and every night he prayed to Tzeentch to reverse the fates of him and his twin. And one night, as Morrslieb was close to the world, the god of change agreed to grant his request.
The next morning, Vilitch woke up to discover that he had melded with his twin, and that Thomin was now naught but an automaton under his command. With enhanced intellect and sorcerous power, he strode out and destroyed his village and killed its inhabitants. From there he hunted down the best warriors of his village and enslaved their minds, making them his puppets.
The End Times
Vilitch did little during the End Times, with Archaon sending him to kill Karl Franz and take Averheim, which he failed to do, and he killed Morbidex Twiceborn off screen. He presumably didn't survive the End Times.