@ Noxvae525 I may have one ; Lucifer is evil, but he and Sam are soulmates, and an ancient legend says that soulmates souls can fuse when in contact with each other (in the cage for example). So their souls become one, and when they separate again, they each have half of the soul from the other ; they now share tastes, feelings (they kind of know and feel what the other is thinking (approximately, like if Luci wants to prank someone or something like that Sam knows it) or feeling), and because of Sam's soul, Lucifer can't dislike humanity anymore and he even considers Dean as his brother. Bonus : Sam has half Lucifer 's grace so half his powers (half human so isn't concerned by angel sigils or blades, same for Lucifer), and when they get bodies on the surface (both outside of the cage), they can still fuse, taking Sam's shape and having a mix of their personnalities (still not affected by angels sigils because of Sam's soul which can "hide" Lucifer's grace).
I hope the description of my idea wasn't too confusing (it was crystal clear in my head but... I know it isn't always for the others ^^'). I hope it'll inspire you !
