A wolf she wants, a wolf she gets

Ash wants a pup, Fenrir, now a prisoner of Azkaban owes her a life debt. Ash doesn't want a relationship, just a pup, Fen will be debt free, a deal is struck. Or is it? For the first time ever this lonely wolf decides he wants more than just a rut & when push comes to shove even the prison walls can't keep him from her. Hello backwards love story. SMUT, consider yourself warned.