The Manitou (Manitou #1)

Phony psychic and conman Harry Erskine never really believed in the occult until Karen Tandy approached him with a rapidly growing tumor on her neck, complaining of dark and disturbing dreams. When the mass is revealed by doctors to contain something living, the stakes skyrocket - not only for Karen and Harry but for all humanity.

Something terrible is returning from the shadows to which it has been confined for centuries - a Native American monstrosity determined to destroy every vestige of the white race that oppressed and preyed upon America’s Indians. And unless a motley group of ill-prepared defenders can harness an ancient native magic, there will be no stopping the malevolent shaman’s terrible rebirth - and no escaping the wholesale carnage it will engender.