"Tyrael was a fool to have trusted me! You see, it was I who told Diablo and his brothers about the Soulstones and how to corrupt them. It was I who helped the Prime Evils mastermind their exile to your world. The plan we set in motion so long ago cannot be stopped by any mortal agency. Hell itself is poised to spill into your world like a tidal wave of blood and nightmares. You and all your kind...are doomed".
Izual after you defeat his demonic form in Diablo 2.
Through his actions Izual may have sealed the fate of Sanctuary. Izual, once Tyrael's lieutenant, led the attack upon the Hellforge to stop the creation of the dark demonblade "Shadowfang". During the battle, Izual was overcome by legions of Chaos. Trapped in the Burning Hells, Izual was tortured. Despite his valor and strength, his form was twisted by the perverse powers of the Prime Evils. They forced him to betray his own kind and give up Heaven's most guarded secrets. Izual became a corrupt shadow of his former self. Izual was confirmed to return in Diablo 3 at Blizzcon 2011.