Looking for a specific fic, it was a sort of Princess Bride au. I know it was a fill for a prompt meme, but I can't remember if it was the kink meme or the angst meme.
Kurt is royalty and his kingdom is invaded by a bad guy (Karofsky or Sebastian, I think?) and he is kept hostage and is being forced to marry the invader. Blaine and Kurt were betrothed lovers, and Blaine was away when this happen. He breaks into the castle as a masked man and rescues Kurt (and Kurt does not realize it's Blaine) and while rescuing him questions him on his loyalty to his first betrothed, thinking it was Kurt's choice to marry the invader and not force. When Kurt reveals he has kept his engagement ring from Blaine because that's who he truly loves and etc, Blaine reveals himself and they live happily ever after and etc.
Kurt is royalty and his kingdom is invaded by a bad guy (Karofsky or Sebastian, I think?) and he is kept hostage and is being forced to marry the invader. Blaine and Kurt were betrothed lovers, and Blaine was away when this happen. He breaks into the castle as a masked man and rescues Kurt (and Kurt does not realize it's Blaine) and while rescuing him questions him on his loyalty to his first betrothed, thinking it was Kurt's choice to marry the invader and not force. When Kurt reveals he has kept his engagement ring from Blaine because that's who he truly loves and etc, Blaine reveals himself and they live happily ever after and etc.