The World Mother. The Sibylline Saga, #3

There he gathers to him the laughing, loving Dark. But restless spirits cannot live on simple human spark. When Gwenna hears a siren call in the night, she travels to a far distant country across the sea to discover its source. There, she encounters the great stone Giants of Lujor and a prophecy that could end it all. There is a hole in the universe - a breach into the void between worlds - and Gwen will do anything to find it before it's too late.
Her search leads her to Amau, where a tightly knit family led by Arlo, called the Dragon, is waging war against the south. But the Dragon's family has a secret, one they've faithfully kept for over a century. And it's a secret Gwen will discover, even if she has to start a clandestine war of her own to do it. Because as terrifying as the Dragon and his armies may be, that's something Gwen has little interest in - just another war among men.
What truly scares her is the lady upstairs, the gentle, soft-spoken wife of the Dragon, with golden hair and eyes as empty as the space between trees.