Harbinger by Ava Marie Salinger

The wheels of Fate have started to turn…

When an unknown plague starts to decimate the Earth, Cassius Black and Morgan King soon realize they’re dealing with something not of the human world. As their allies gather in San Francisco to try and determine the cause of the contagion, unwelcome news reaches Morgan’s ears. The Dryad kingdom has come under attack by an unknown enemy.
Forced into making a difficult choice, Cassius and Morgan part ways to deal with both crises. But the battles in Ivory Peaks and on Earth end up costing the couple more than they could ever have imagined, bringing them face to face with powerful enemies from their past. On the edge of despair, Cassius finds hope in the arrival of an unexpected group of deities. Goddesses who are related to both Morgan and Victor Sloan by more than just Fate.
Cassius learns of the twisted threads of destiny that bind them all and discovers the latest peril they face is of Elios’s making. When he’s told by the Goddesses that the only way to end the God of Darkness’s deranged scheme is to find a legendary item lost to the tides of time, Cassius vows to stop at nothing to locate it, whatever the sacrifice.