The Fallen Angel
There is a dark, tortured soul who was trapped within this forsaken realm long ago. He was called Izual by mortal men, and in ages past he was my most trusted Lieutenant.
Yet, against my wishes he led an ill-fated assault upon the fiery Hellforge, itself.
Despite his valor and strength, Izual was captured by the Prime Evils and twisted by their perverse power. They forced him to betray his own kind and give up Heaven's most guarded secrets.
He became a corrupt shadow of his former self - a fallen angel trusted neither by Heaven nor Hell.
For his transgressions, Izual's spirit was bound within the form of a terrible creature which was summoned from the Abyss. His maddened spirit has resided within that tortured husk for many ages now.
It seems to me that he has suffered long enough. I implore you, hero, find Izual and release him from his cruel imprisonment.
Put an end to his guilt and suffering. - Tyrael
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 own 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 forth into your world like a tidal wave of blood and nightmares.
You and all your kind... are doomed. - Izual
Thank you, hero, for putting Izual's tortured spirit to rest. May the Light protect you and the powers of Heaven shine upon your path.
But, if what you tell me is true, then I fear that we have been played for fools all along.
Izual helped Diablo and his Brothers trick me into using the Soulstones against them... Now the Stones' powers are corrupted.
With the combined powers of the Soulstones under their control, the Prime Evils will be able to turn the mortal world into a permanent outpost of Hell! - Tyrael