Izual

Izual is one of the villains from Diablo, and the catalyst of all the events in the game.

Story
Izual was a lieutenant of the Archangel Tyrael, known as the greatest hero of The Great Conflict. Carrying the holy blade Azurewrath, he won countless battles for the heavens. After he learned that the forces of hell were forging the dark blade Shadowfang, he took upon himself the duty of destroying the cursed blade. Against Tyrael's advice, he led an assault against the Hellforge, which ended with his troops being completely annihilated and his capture. What Tyrael didn't knew was that this was Izual's plan all along. Fed up with the Great Conflict, Izual sided with the powers of Hell and shared with The Great Evils his knowledge. He told the Prime Evils, Mephisto, Baal and Diablo the secret of the Soulstones: if their souls were imprisoned in a Soulstone, they could possess a mortal and use him to channel their full powers into the mortal realm, thus being able to reach the Worldstone, the source of the Soulstones and the artifact that held the balance over the world of Sanctuary. If they could corrupt the Worldstone, then they would ultimately prevail against Heaven. Thanks to Tyrael's foolishness, everything goes as planned and the three Prime Evils are able to manifest themselves into the mortal realm. As an adventurer follow Diablo and his brothers, he enters the Burning Hells aided by Tyrael, in order to find and kill Diablo. Tyrael asks the hero to kill Izual and save his soul from the forces of hell. The hero finds Izual in the Plains of Despair and slays him. The soul of Izual tells him that they were playing for fools all along, since everything was his plan.