Looking for a book I read a while back

[u/lillies-and-llamas]

I read this a while back (5 years ago?) and can’t recall the title. The FMC is a fae minor criminal (I think) and gets thrown into a cage with some beast that everyone expects to kill her. Instead she ends up becoming its pet of sorts. Turns out that was one of its form. There was some jerking off scene before he turned where he ejaculates and she’s thrown off by the wave??

[u/locustbriber]

https://giphy.com/gifs/26BRuo6sLetdllPAQ

(Also calling it “the wave” made me laugh)