On Torn Wings by A.L. Kesslet
Dark War Chronicles #3
Danielle is on a mission to take down a killer, when all signs point to vampire she recruits Orion to help. Bribing him with information on the Fae Queen who stole his crown takes her further into the supernatural world than she wanted. Working side by side, they start to realize there is more there than a forced work relationship, but Orion is still pining over the disappearance of Tegan.
A missing human
Tegan’s kidnapping is taking a toll on the whole territory, Lucius is losing his sanity and the war has taken a turn for the worst. Fed up with the chaos Orion seeks to escape the territory, but other than death there’s only one other option —taking back his crown. After centuries of working under the vampire Danielle offers him the chance and ability to take his rightful place.
Goodreads link: https://www.goodreads.com/book/show/22233992-on-torn-wings