In the Pre-Crisis reality, billions of years ago, a Maltusian scientist named Krona, performed a forbidden experiment in an effort to see the origin of the universe. His irresponsible actions disrupted the process of cosmic creation, resulting in an additional, opposite universe of pure evil. Its own existence corrupted millions of planets in the Positive Universe.
In all known worlds contained in the antimatter universe, its inhabitants glorify evil. Magic can't exist (directly at least) into antimatter universe; due it the Earth's sorcerers have not followed other heroes to ambush Antimonitor in his headquarters. 
The Antimatter Universe is also the location of the planet known as Qward. The Weaponers of Qward - devoted adversaries of the Guardians of the Universe have frequently crossed swords with their dimensional counterparts, the Green Lantern Corps. To aid them in their efforts to destroy the Guardians, they have frequently relied upon the aid of a former Corps member, Sinestro. After Sinestro reneged on the Green Lantern Corps, he was banished to this universe, where he was popular among the Qwardians, even winning some of their annual contests of cruelty.
The cosmic being known as the Anti-Monitor is also indigenous to the Anti-Matter Universe. An analog to the universal Monitor, the Anti-Monitor attempted to destroy all reality with a wave of pure antimatter energy. This ambitious attack culminated in what has become known as the Crisis on Infinite Earths.
During the crisis, it was discovered that Alexander Luthor, the orphaned son of Earth-Three's Lex Luthor and Lois Lane was a being comprised of both Antimatter and normal matter. As such, he could function equally in both realities, without undue stress.
Shortly after Crisis it was stated that the Crime Syndicate were Thunderers but after Zero Hour the Crime Syndicate of Amerika of the antimatter Earth appeared.
In JLA/Avengers the antimatter reality is destroyed by Krona. In Syndicate Rules it is revealed it was reintegrated anew by sources unknown but it is not a entirely faithful reintegration. Owlman discovers that the antimatter universe is now only months old.
Points of Interest
- Qward: Planet of the Thunderers and Weaponers of Qward.
- Qward's Moon: Antimonitor was born here a few billion years ago.
- An Earth duplicate: Here lives the Crime Syndicate of Amerika. 
- During the Crisis on Infinite Earths the Anti-Monitor absorbed the anti-matter energy of over a million worlds in his reality destroying them.
- Anti-Matter Man
- Sinestro Corps
- Weaponers of Qward
- Thunderers of Qward
- Crime Syndicate of Amerika
- At the end of Crisis on Infinite Earths the Anti-Monitor's fall back into one of the binary suns creates a shockwave that destroys everything for millions of miles including Qward and the moon on which the Anti-Monitor was born.
- It is unknown if there has been more then two reboots/rewrites of the antimatter universe. Qward continued to appear even after being destroyed during the events of Crisis on Infinite Earths #12.
- Appearances of Antimatter Universe
- Location Gallery: Antimatter Universe
- Catalogued images related to Antimatter Universe
Links and References
- Negative Zone for Marvel Comic's version of the Antimatter Universe.