The Dark Vale. The Tuonetar Cycle, #3

Peylan rises from the ashes of war, but peace is a fragile illusion. In the alleyways of the great metropolis, the living dead, crime lords, and power games defy every human law. Vidar the Pyromancer brings fire where others bring words - and when grief breaks his soul, there is no wall thick enough to stop him. Far from the city's smoky streets, Kaia the Valkyrie discovers that the hardest battles are not fought with a sword.
Elected Queen of the Steppes among the nomadic tribes of Tiros, she must quickly master the arts of seduction, deception, and political survival - or fall prey to a war waged between the sheets long before it reaches the battlefield. And then there is the Vale: a forgotten castle in the mountains of the North, guardian of secrets no one was meant to find. Vidar, Harald, and their companions arrive seeking answers.
What they find calls into question faith, loyalty, and the ever-thinning line between the living and the dead. For Tuonetar does not forget. And her vale has many doors - yet none lead where one expects.