At the same moment that the universe was born, the antimatter universe was also created. Billions of years later, the being known as the Anti-Monitor began taking power. He conquered the weaponers of Qward, and from them he learned there was a different universe, a positive matter universe, and he wanted control of it, too. Little is known about the Anti-Monitor's life before The Crisis began. He is believed to be The Monitor of the Anti-matter Universe, the Anti-Monitor was responsible for the original Crisis on Infinite Earths.
After a cosmic accident tore a hole between the positive and antimatter universe, antimatter began flooding the universe, resulting in the interdimensional "crisis." It took Earth's greatest heroes to stop the Anti-Monitor. The Monitor with aid of the Harbinger gathered these heroes from different times and different worlds to bring down the Anti-Monitor.
The Psycho-Pirate was one of the selected and was quickly overtaken by the Anti-Moniter. He also sent his shadows demons to stop the others that were summoned. One of these infiltrated one of the Harbinger's bodies and controlling her to assassinate the Monitor. After this the Anti-Moniter thought he had won but his counterpart had already set things in motion.
This carefully laid plan had it's cost. Supergirl in a one on one match with the Anti-Moniter was killed. This nearly killed the Anti-Monitor as well. He eventually made a new suit and began using the Quardian Warriors to build a cannon that would finish destroying the last five universes. Flash: Barry Allen was able to destroy the cannon but only at the cost of his own life. In the end it was the sacrifices made by the Superman of Earth-Two, Superboy-Prime and Alexander Luthor of Earth-Three that resulted in his death.
