Midnight Auction. The Midnight Auction Series, #1

Magic has a market. The cruelest thing it sells is your name. In the cities of the Binding, the Midnight Auction trades true names - and whoever speaks yours owns you, body and will, for as long as they live. Lira Vess goes to the Auction to sell the last memory of her dead mother. She leaves having spent everything to buy a stranger's name instead - so that no crueler hand can hold it. Now she owns Nox Severin: the most dangerous man alive, reduced to a single word in her mouth.
Betrayed into the chair by the one friend he trusted, he is waiting for his new owner to finally use the leash. She won't. Not to save her shop, not to save her life, not with a blade at her skull. She means to give the name back - though the market swears it cannot be done. But the bond between them is changing, running both ways and then backward, and the people who built the market are beginning to fear that a healer they priced at nothing may be the only thing alive that can unmake every leash they own.
He's bound. She won't pull the thread. And he is already, quietly, choosing her. The Midnight Auction is Book One of a slow-burn, closed-door romantasy series - for readers of fated bonds, morally grey heroes, and found family. Worldbuilding-deep, heart-first, and the door stays closed.