Apocalypse is an Ultra Boss unlocked after defeating 1000 monsters in the Plaguelands.
It's a purple and black version of the Plaguebeast.
It acts similar to Plaguebeast, but seems to "charge" at you more, and with far greater speed. It also shoots out small purple projectiles in an angle up and down. It seems to shoot about 4 at a time. A ranged build is greatly recommended.
Melee/Contact Damage: 100
Drops two Apolalypse A rather than the full armor set (Similar to how Ironclad drops two Ironclad H)