Taken By the Beast by Jenna Kernan

The fourth and final book in this thrilling epic fantasy romance series pits all four soulmate shifter couples against the army of undead in an epic battle for the living world.
The only thing more dangerous than seeking the protection of a beast is falling in love with him.

When the first born of the spirit children and shapeshifters comes of age, Samantha Proud unlocks her powers to send evil ghosts back to the spirit world. But her gifts provoke a powerful foe, determined to use his army of undead to conquer the living world. To survive she seeks a frightening protector.

The danger of Alon’s ominous powers have kept him from ever loving a woman but protecting Samantha is a temptation he cannot resist. Can her claim that they are soulmates be believed? To give in to his desires may prove as deadly to her as to her enemies. But deserting Samantha will leave her defenseless. Tortured by his need to have her and longing to keep her safe, he must choose which course is the greater risk to the only woman he has ever loved. As their enemies amass and with victory in doubt, his desire for Samantha tempts him to expose his dark secret. Will the truth destroy their soulmate bond?