Background

The specifics of The Eidolon's origins are unknown, but it has been revealed that he was once a normal man who, for some reason, was unable to die. When his time came, instead of passing on, he wandered through places between life and death but found nothing there. He somehow made his way back to the land of the living and made it his mission to spread the word that there is no God and faith in him is foolish and without meaning. In addition to delivering this message, he tasked himself with meting out punishment on those who make life hard for others since this is all anyone gets.

Change or Die

During the Change or Die arc of Stormwatch, The Eidolon was a member of the Changers. He had joined the group in the 1990's because he agreed that their plan to change the world was right, and also because The Doctor and Engineer of that time had promised that they could give him the death and peace he was looking for. When Stormwatch encountered The Changers, Eidolon was killed by Rose Tattoo, the spirit of murder.

Number of the Beast

Recently it was shown that The Eidolon hadn't really (permanently) died. Instead, he was one of the two Changers to have survived Stormwatch's attack (the other being The High) and was placed in a special virtual reality environment along with at least 666 other former SPBs that disappeared during WW2. For a long time the other heroes and villains believed the city they lived in to be real, but The Eidolon always knew it was artificial. He tried to warn them but they just thought he was crazy. When The High's body (what was left of it) was put into the virtual city though, Eidolon was able to get him to figure out what was going on and free the others.

World's End

After the end of the world, The Eidolon leads an enormous group called The Army of the Mad. Most, if not all, of his army is made up of criminals of the worst kind and they go around terrorizing everyone they can find under his orders.