You Promise(d) Me - Loki Laufeyson
Shapeshifter ends up in the same cell as Loki, who's already been imprisoned for his crimes after the events of Avengers. ✦ ✦ ✦ ✦ ✦ A/N: I have been writing (but mostly imagining) this fic since Endgame came out, so I will say that this story has gotten out of hand on multiple occasions so I'm warning y'all before you...