Realm of Nightmares by Hillary Raymer

Magic. Fae. And morally grey.
Realm of Nightmares is the exciting third installment of the Faeven Saga…

After a faerie bargain goes wrong, Maeve Ruhdneah finds herself stuck in the realm of the Ether, separated from everyone she loves. Knowing she’s running out of time before Parisa attacks, Maeve develops a plan—venture to Diarmavh and gain the favor of the Wild Hunt, then make a deal with the god of death to return to Faeven. Unfortunately, Aed isn’t too keen on releasing her and worse, Maeve’s magic is failing. The longer she stays, the more she continues to lose. But a familiar face threatens to upend all she’s working toward, and as secrets from her past are revealed, the thread tying Maeve to Tiernan slowly unravels.
In Niahvess, all of Tiernan’s worst fears are being realized. Faeven is dying. Maeve has yet to return from the Ether. And again, he must make the treacherous journey to Maghmell to save all that he loves. Except this time, the goddess of life is nowhere to be found. As the Four Courts begin to crumble, Tiernan is to forced look beyond the borders of Faeven for help. But as Parisa’s forces grow, the lifeblood of magic continues to fade, threatening to plunge the realm into darkness forever.