Riders of Chaos. The Seventh House, #4

It is said that a former best friend makes the worst enemy, especially if that friend has connections into other dimensions, and resurrects the most malevolent woman that ever lived. Ankerita Leighton is living the life of a recluse when a subliminal message, coupled with an unseasonal heat wave, tempts her to leave the safety of her home. Now vulnerable, she is tormented by demons, both supernatural and human, released by this new evil.
She teams up with a witch and the once and future king, to tackle threats to a world, teetering on the edge of Armageddon. If they fail, the new Horsemen of the Apocalypse will infiltrate world powers at the highest level, and lay waste to all creation.