Armageddon is the overarching antagonist of Chaos! Comics, first appearing in the 1999 Miniseries Armageddon.
In the inconceivable chaos that existed before the current universe, a race of people known as the Chaos Lords reigned. They engaged in creations the likes of which not even the most pretentious Young Gods could imagine, living in Chaos and anarchy.
Eventually, one of their member, Armageddon, decided that he didn't like the way the other Chaos Lords Created, and decided to enslave them all for his own goal: total entropy. Eventually, 6 Chaos Lords joined forces to fight him: Genocide, Lucifer, Kreator, Jehovah, Odin, and Brahma. Their battle was of such intensity that it destroyed the entire universe and created another in its steed, seemingly killing Armageddon.
In 1999, Heaven, Lady Death, and Hell were in a war that ravaged the Earth, when another participant emerged. Armageddon came to Kansas, choosing Earth as his first target, as it was the center of The Nexus of All Things. While Evil Ernie vehemently refused to obey the monstrosity, Purgatori was more than willing to serve as its thrall (if only to betray him later). Armageddon then launched a campaign of Nihilism, attempting to destroy everything that ever was or would be.