Castle of Nevers and Nightmares by Lana Pecherczyk

If you’re not pretty, you’re a Nightmare.

When winter comes to the Court of Dreams, the war against the Subterranean of Nightmares freezes. To celebrate, the faerie queen holds a tournament where mortals compete for the prize of a dream come true. For outsider Willow Nightstalk, it’s the only way to break the curse making her as ugly as she feels.
But the deadly tournament has a darker purpose—to flush out flawed mortal blights on the perfectly pretty fae society… and to kill them. Any left alive are conscripted when war returns in spring. When the coveted prize can give you anything your heart desires, allies are likelier to stab you in your sleep than save you.
Surviving means securing the highly contested patronage of the powerful fae nobility. But when the notoriously recluse House of Shadow is the only option left, the odds are stacked against her. Especially since it’s led by the six beautiful fae boogeymen who ruined her life. Then, the unthinkable happens.

For the first time in years, the House of Shadow chooses a protégé. Her.
Nothing is as it seems in the Court of Dreams, least of all the Nightmares.