This is the third in the "Godspeaker" trilogy, starting with Empress, then The Riven Kingdom.
Hekat and her Mijaki warhost are annexing more and more of the known world to Mijak, after conquering the desert. In Ethrea Rhian is now Queen and is aware of the threat from Mijak.
The novel covers Rhian's preparations for a war that could mean the end of "religious freedom" and personal freedom. After the preparations are complete the following clashes are covered. No! I won't say who prevails, you'll have to read the books to find out. In this book Zandakar finds out that Vortka is his true father, a fact the reader has known from his conception in Empress. The Scorpion Knife also reappears. I think that if Miller had made Hekat a less motivated character most readers would have abandoned the trilogy after the first book, she also makes sure that Hekat gets under the reader's skin before she becomes strongly driven.
If you like fantasy I would thoroughly recommend the trilogy.