Deyacadem Cycle: Rise Of The Forgotten God

From the back cover:

There is a darkness that hangs heavy over the hill-country. Shadows form where once there was light. Abominations not seen in the Eight Lands for centuries rise out of the mists, take cattle and children, sometimes hunt even grown men in the night.

In the midst of it all, a lonely soul tracks through the snow, seeking her stolen sister. Armed only with the legacy of her family, a blade cut from light and spirit, Zulya Deyacadem must challenge the might of a mage named Felgath, fight off the ravenous hordes of rattling shades that hunt her, and stand before a terrifying beast of blood and wings, an elemental evil whose name is never even breathed, except in shadows and curses.

Based on the episodic saga Arkenstride, Rise of the Forgotten God brings the entire series together in the first third of the book, then picks up where the series left off, adding twenty-seven new chapters of adventure to round out the first major installment in The Deyacadem Cycle.

Sisters In Slaughter (book 2)