Archangel's Heart: Book 9 by Nalini Singh
One of the most vicious archangels in the world has disappeared. No one knows if Lijuan is dead or has chosen to Sleep the long sleep of an immortal. But with her lands falling into chaos under a rising tide of vampiric bloodlust, a mysterious and ancient order of angels known as the Luminata calls the entire Cadre together to discuss the fate of her territory.
Accompanying her archangel lover Raphael to the Luminata compound, Guild Hunter-turned-angel Elena senses that all is not as it seems. Secrets echo from within the stone walls of the compound, and the deeper Elena goes, the uglier the darkness. But neither Raphael nor Elena is ready for the brutal truths hidden within - truths that will change everything Elena thinks she knows about who she is . . .
Nothing will ever be the same again.