The Titan

The Titan refers to an acient demonic entity, of enormous size and strength, born form the bowels of hell, created by the dark lords to defeat the Doom Slayer. Their plan failed, and in an unknown age the Titan was felled by the Doom Slayer. The corpse of the Titan still remain in the Great Steppe, and non-significant amount of deterioration has occured, and demonkind has used the body to build temples and rooms into the beast's internal structure. The Titan directly drew strength from the countless demons killed by the Doom Slayer and what is interesting is that the Slayer received his upgraded praetor suit after the Titan was felled. The Titan is perhaps the largest demon to ever be in existence, second to the Icon of Sin, although this is unconfirmed, as we can only see the head of the Icon.

History
In response to the evergrowing threat of the Doom Slayer, the Lords of Hell decided to create a demon strong and large enough to defeat him, and thus the Titan was born, and soon he faced the Slayer. He drew strength from every demon killed by the Slayer and a great fight ensued upon the Umbral Plains. Both sides fought for some time, until the Titan was killed and unlike other demons, his corpse did not burn away and remained embedded into the Umbral Plains, and is presumed it will remain in the Hellscape until the end of time or Hell.