Four dominions - Eric Lustbader

The End of Days has been predicted for the last two thousand years, but now it is upon us. A secret war was raged for millennia, a bitter conflict as old as time itself: the battle between Good and Evil. Brother and sister Emma and Bravo Shaw now stand at the epicentre of the confrontation, for they possess the only copy of The Book of Deathly Things - the fallen Archangel Lucifer's first and last Testament. While Emma and Bravo struggle to decipher the book's dreadful secrets, Lucifer's advance guard, the Fallen, are awakening. Should they can reclaim the Testament, Humankind will be irrevocably enslaved by the forces of evil. Time is running out, leviathan is coming, the apocalypse is nigh.