Deyacadem Cycle: Sisters in Slaughter

From the back cover:

In the far east, a woman kills three men with her bare hands.
In Tetidalia, a traveling justice comes to a small town seeking to save a long lost comrade.
At the far north end of the world, a single sister calls an ancient evil from the ice with blood, with slaughter.
And in a tower cloaked in ice, another sister waits for the release she knows is only days away.

Sisters in Slaughter is the second book in E.S. Wynn's Deyacadem Cycle and the sequel to Rise of the Forgotten God.

Rise of the Forgotten God (book 1)