Dreamslayer was a member of a group of supervillains.
During his team's battle with the Justice League, Dreamslayer managed to subdue both Batman and Vixen, but was trapped in a bubble by John Stewart. He used his pyrokinetic abilities to try and overcome the bubble, but all it did was consume the oxygen inside and render him unconscious.
In the DC Comics, Dreamslayer is a demonic entity that is actually feminine, but assumes a masculine appearance, with her own religion and worshipers. Like the other Extremists, she is based on a character from Marvel Comics; in Dreamslayer's case, she is based on Dormammu, the archenemy of Doctor Strange.