Found! (Dean Winchester)
I am looking for a fic in which Dean is caught by a monster that requires sex to survive. He is trapped in a cage and the monster tries to reason/build a peaceful relationship based on Deans acceptance. Disobedience is still punished and the sex is noncon.
If I remember correctly, Cas gets abducted as well while looking for Dean.
I can't for the life of me remember the type of creature or where I read it.
Does this sound familiar to anyone?
Edit: Found in comments! It's "The Bone Eater". Thank you so much, nicky69!