Dragon's Gift: The Dark Fae, book 1: Trial by Fae
Linsey Hall et Veronica Douglas2019

He must never realize who I am.

I'm a demon slayer, so I lead a simple life slaughtering monsters. As long as no one learns that I’m descended from a forbidden line of Dragon Bloods, I can keep my job and my life.

But when a powerful Fae king realizes I’m his fated mate, I’ve got problems. Especially since A), he hates me and B), he learns my secret, and it puts my whole life at risk. I want to kill my mate.

The stars align when my employers send me to the Fae kingdom to compete in the Trials of the Fae as an undercover agent. My real goal? Investigate the king for the murder of hundreds.

But the king only has eyes only for me, even when I’m in disguise. He senses that I’m his mate, and our attraction is off the charts. No matter how much we mistrust each other, we can't stay apart. But when he realizes what I’m up to, there will be hell to pay. That is, if I survive.