All Hallows Game by Leigh Kelsey

Nightmare wants me broken, and she’ll use the men I love to break me.

Death. Misery. Torment. The three gods I was cursed to marry when a cult took over my med school’s Halloween party. I’ve experienced each one of those traits in the past week: the death of my best friend, the misery of being unable to save him, and the torment of knowing the murders are far from over.
Nightmare thinks she’s won. She’s driven a Cat-sized wedge between Death, Miz, and Tor, but I refuse to let that power-crazed psychopath win. But Ford’s End is more dangerous than ever, and with no way off the island, my surviving friends and I have no choice but to obey Nightmare and plan her downfall in secret.
But Nightmare has planned this game for hundreds of years and she has more than one trick up her sleeve, with more cruel surprises for me. Byron isn’t the only person helping her torment us.
If I’m going to survive, I’ll need all three of my deadly husbands. The only issue? Two of them hate me, and the other isn’t sure his feelings are real.