Nephilos

Nephilos is an ancient being who was summoned by "witches" during colonial times to grant them powers and curse their enemies. He delighted in violence and torturing his victims. Josephine Young made a pact with him to gain immortality, and later sealed him away to use him as a source of power in the future. In the present day, he is forced to attack Mirror Face under the orders of Josephine, although he only maims and does not kill it.

Nephilos is later stolen from Josephine and placed in a data prison by a newly recovered Mirror Face, where he is tasked to track down information on the Weird Brothers and the Hartford witch trials. The process erases his memory and he forgets his original bloodlust, instead trying to save the people Mirror Face has marked for death. He is horrified when he learns the truth, but is unable to prevent himself from claiming Josephine's soul after Mirror Face kills her. He ends up siding with Mirror Face to track down the Weird Brothers and earn his freedom again.

He has no body in the dataspace, but manifests in the real world as a tall figure in a low hat and a black leather jacket. Mirror Face calls him a "possessor" because he can infiltrate living and nonliving things to exert his influence. He ends up being turned into a virus to infect Mirror Face's readers and make them into sleeper agents to hunt down Shaun and Tom.

He appears in the "gallows hill" series.