Demon Knights Vol. 1: Seven Against the Dark — Paul Cornell

Set in the Dark Ages of the DC Universe, a barbarian horde is massing to crush civilization. It's fallen to Madame Xanadu and Jason Blood, the man with a monster inside him, to stand in their way--though the demon Etrigan has no interest in protecting anyone or anything other than himself! It'll take more than their own power to stop an army fueled by bloodlust and dark sorcery, and some very surprising heroes--and villains--will have no choice but to join the fray!

This volume collect issues 1-7 of Demon Knights, part of the DC Comics -- The New 52 event.