Slayer's Testament as written within the Corax Tablets of Hell, chronicled within the Book of Vile Darkness

From the first age, the first battle, when the shadows first lengthened, one will stand. Burned by the embers of Armageddon, his soul blistered by the fires of Hell and tainted beyond ascension, he will choose the path of perpetual torment. In his ravenous hatred he will find no peace; and with boiling blood he will scour the Umbral Plains seeking vengeance against the dark lords who wronged him. He will wear the crown of the Night Sentinels, and those that taste the bite of his sword will name him... the Doom Slayer.

Tempered by the fires of Hell, his iron will shall remain steadfast through the passage that preys upon the weak. For he alone will be the Hell Walker, the Unchained Predator, who will seek retribution in all quarters, dark and light, fire and ice, in the beginning and the end, and he will hunt the slaves of Doom with barbarous cruelty; for he will pass through the divide as none but fiend have before.

And in his conquest against the blackened souls of the doomed, his prowess will be shown. In his crusade, the seraphim will bestow upon him terrible power and speed, and with his might he will crush the obsidian pillars of the Blood Temples. He will set forth without pity upon the beasts of the nine circles. Unbreakable, incorruptible, unyielding, the Doom Slayer will seek to end the dominion of the dark realm.

The age of his reckoning will be uncounted. The scribes will carve his name deep in the tablets of Hell across eons, and each battle will etch terror in the hearts of the fiends. They will know he will come, as he always had, as he always will, to feast on the blood of the wicked. For he alone will draw strength from his fallen foes, and ever his power will grow, swift and unrelenting.

None will stand before the horde but the Doom Slayer. Despair will spread before him like a plague, striking fear into the shadow-dwellers, driving them to deeper and darker pits. But from the depths of the shadow will rise The Great One, a champion mightier than all who had come before. The Titan, of immeasurable power and ferocity. It will stride upon the plain and face the Doom Slayer, and a mighty battle will be fought on the desolate plains. The Titan will fight with the fury of the countless that had fallen at the Doom Slayer's hand, but there the Titan will fall, and in his defeat the shadow horde will be routed.

And in his terrible rancor between worlds and through time, the Hell Walker shall find the wretch who shall not be named, but in his heresy remain loyal to his evil cause. The wretch will adorn the Doom Slayer in a mighty armor, wrought in the forges of Hell, impenetrable and unyielding. With sword and shield of adamantine strength, the Doom Slayer will set to banishing all that were left unbroken by his savagery to the void.

Yet as the mighty Titan falls and dread engulfs the armies of Doom, the demon priests of the Blood Temples will lay a trap to capture this scourge of Hell. Insatiable, even by the vanquishing of the Great One, the Hell Walker will seek prey in the tombs of the Blood Keep. And blinded by his fervor, the lure will draw him in. The priests will bring down the temple upon the Doom Slayer, and in his defeat entomb him in the cursed sarcophagus. The mark of the Doom Slayer will be burned upon his crypt, a warning to all of Hell that the terror within must never be freed. There he will lie, still, and ever more, in silent suffering. And woe to all darkness should he be released again.

For he will walk among them, and he will smite the evil from all realms. For he who comes in their time of need is not of mortal breed, he is the Destroyer, the right hand of the Creator and the one who brings fear where there is no hope.'
-Corrax Tablets, 1-9, Infernal prophecy