The Gamma Corps has been created by General Ryker. He has taken samples of the DNA of the Hulk, Doc Samson, the Leader, the Abomination, and the Harpy and added them to soldiers that hate the Hulk. They possess powers similar to those whose DNA they share and are to be the one force that can take him on.
The Gamma Corps was created by Frank Tieri and Carlos Ferreira and first appeared in Gamma Corps #1.
The original Gamma Corps team were brought together by John Ryker and consisted of Grey, Griffin, Mister Gideon, Prodigy and Mess. Later, Ryker assembled a second team of Gamma Corps to track down and capture Lyra, this (all-female) team consisted of Aberration, Axon and Morass.
Major Story Arcs
World War Hulk
The Gamma Corps seemingly killed Flux and then fought the angriest version of the Hulk during World War Hulk. They lost and were betrayed by General Ryker, and had to flee.
In hiding they began bickering with each other knowing that inevitably they would be arrested and possible killed. They were surprised when Iron Patriot himself came to them (though they first mistook him as Iron Man). Prodigy was about to telepathically/telekinetically kill them before Osborn was able to explain that he was only there to recruit them. He then made them HAMMER's secret bounty hunters.