The Nineveh Codex
The Nineveh Codex was a book that included a summoning ritual.
Troy Wilkinson and his friends attempted to summon a creature described in the book. Called an Achamoth.
They desecrated the grave of Maxime Gordon (with a crude ritual slaughter of a dog) prior to her burial to ensure that the Murderess was buried on unconsecrated ground.
They later broke in and dug up the grave severing her left hand and using it in the ritual that the codex sid would grant them great power and their hearts desires.
Unfortunately for Troy, the book did not mention what would happen if the person involved was not actually guilty of the murder. The creature summoned possessed Troy and made him invulnerable to "The Strange" and "Any weapon forged". Without translating the remainder of the book the team left to stop Troy as soon as possible. The possessed Troy killed his two friends messily and fled the scene, apparently uninterested in the cops.
Troy carved a path striking at several locations including the Basement of the abandoned appartments and
They finally caught upto him at a Rave in a converted church called Paradise. Where they attempted to subdue him, and then kill him with weapons, however he was almost immune to their attacks,
He finally talked, expressing an urge to destroy "The Strange", which Burl and the others had few problems with. He was let loose to prevent further loss of life and fled out to where Bishop was chasing a Blur Suspect.
Troy horribly burnt Bishop before chasing off after the Blur himself.
Troy's body was found the next day, dessicated and brutally damaged.