Deadmen

Deadmen (デッドマン, Deddoman) are people who are infected with the Nameless Worm which enables them to do extraordinary things with their blood. Most of them were infected during the Great Tokyo Earthquake.

Ganta Igarashi is an exception for he was infected much later by a unique Nameless Worm by the Wretched Egg herself, during the Nagano school massacre. He became a Deadman with a unique ability, that is the key to the Mother Goose System.

During the Great Tokyo Earthquake, pieces of a certain Red Diamond were found. The Deadmen yet to come somehow inhaled or swallowed a piece of the Diamond. The Red Diamond is a capsule for the Nameless Worm and so the Nameless Worm settled in the bodies of the Deadmen and gave them the Branches of Sin. Those Nameless Worms were somehow created or released by the Wretched Egg.

Capture
The privately owned prison, Deadman Wonderland, is a facility where Deadmen are held (more specifically the G Ward). They are used to compete against each other in the Carnival Corpse. Tsunenaga Tamaki did research on the Nameless Worm and was able to create artificial Deadman: the Forgeries from data he thought he obtained from Hagire Rinichirō's computer. The Forgeries' powers are based on a supposed Anti-Wretched Egg poison. This, however, turned out to false as the real data was hidden.

After Makina overthrew Takami and shut down Deadman Wonderland, all the Deadmen had a re-trial. Those who committed actual crimes were transferred to a normal prison (like Minatsuki Takami and Chaplin Sukegawa) and those who were innocent were released in the outside world (such as Senji Kiyomasa and Ganta Igarashi), though many could not adjust to a normal life.