Goetia: Book of the Watchers
Forty-nine years ago, followers of a Satanic cult built the Teufel Manor. After the cult's mass suicide in the Manor, the building was seen as cursed, and no one would dare step foot on the property, much less purchase it lest they disturb whatever foul spirits the cult wrought forth. That is, until skeptic Henry Cox and his wife, Tasha bought the place as a home for their growing family.
The year is now 2009. It has been forty-nine years since the cult began their dark work. The Cox family has grown, with their twin daughters Ashlin and Dakota, and a son, Xander. And it's the day that the gears of a plan that spanned millenia slowly begin to churn to change the world forever, starting with the Cox family.