Well I’m probably not the first person to think that Loki/Castiel would be a great pairing but I am the first to call it Lostiel.
(I just went into the Loki/Castiel tag and I’m the first person to have submitted anything to that tag…So maybe I am the first person to have thought of the pairing O.o)
Anyways, as to what made me think of the pairing: Honestly it’s because there are so many similarities between Loki and Castiel. They both think they are part of a family and then are basically told otherwise. And they aren’t sure how to handle that because they have done so much for that family. They both become determined to prove themselves and they both seek out power as a way of doing that. However, Castiel gives up his power because he learns he was wrong. Loki was so certain he was right that he turns evil.
I guess that is also part of why I ship it, now that I think about it.
The only way to explain why I ship it is to give a sort of timeline of how I think their relationship would play out. We already know that the norse gods exist in the world of Supernatural, so having Loki and such in the Supernatural storyline isn’t as far-fetched as some might think. We know that Gabriel took the identity of Loki as a witness protection sort of thing. Whose to say that Loki didn’t let him borrow the identity. After all, Loki isnt on good terms with the people of Asgard so why not give up his name for a little bit. He’s the god of Mischief, surely he would find it an amusing prank.
Anyways, I believe that Loki (the Avengers Loki) would pop up as a villain the Winchesters have to face. Naturally Castiel would appear to try and help the Winchesters and Loki would find it amusing and sort of disgusting that such a strong creature is a puppet to the Winchesters.
So Loki would engage Castiel in tests. He’d try to manipulate Castiel into leaving the Winchesters. He would lie and use his silver tongue to try and show Castiel that he is nothing to the Winchesters but a tool. Then we would come to the point where Castiel decides to work with Crowley to open the door to purgatory. And Loki would appear once in a while, say something along the lines “And how do you think your puppeteers will react when they learn their puppet has broken free of his strings?” And Castiel would argue that Loki was wrong; that the Winchesters wouldn’t like what he was doing but wouldn’t argue because they had done the same in the past. Of course Loki ends up being right, the Winchesters are pissed and basically disown Castiel. And Castiel starts to wonder what else Loki was right about. He starts to trust Loki and Loki keeps playing Castiel.
Their relationship would be twisted and dark and unstable. Yet there would be a strange comfort between them because they both understand what the other is going through. I don’t think there would ever be love, but there would be some strange twisted form of respect.
I hope that helps, anon. Feel free to ask me anything else you wish to know.