In the first age, in the first battle, when the shadows first lengthened, one stood. He chose the path of perpetual torment. In his ravenous hatred he found no peace. And with boiling blood he scoured the Umbral Plains seeking vengeance against the dark lords who had wronged him. And those that tasted the bite of his sword named him... The DOOM SLAYER Tempered by the fires of Hell, his iron will remained steadfast through the passage that preys upon the weak. He set forth, without pity and hunted the slaves of Doom with barbarous cruelty. Unbreakable, incorruptible, unyielding. None could stand before the horde, but the Doomslayer, for he alone... was the Hellwaker.

This will show you the Doom Bible