Falcon & The White Wolf
Sam Wilson made a deal with a devil and had resigned himself to paying the price—until said devil made the mistake of giving him someone new to live for. Freedom is a foreign concept, and the healing process is slow, but Bucky and Sam have long since proved to themselves and each other that together they can make it through anything, even if it means facing their fears—both of the wizard who kept them prisoner, and of the love each shares for the other.
Or
A fantasy AU where Sam has wings, Bucky can shapeshift, and they both have a bone to pick with the wizard who made both their dreams and their nightmares come true.