Approximately an age ago, somebody on my Tumblr dash asked a question about fics to which this was the answer. I couldn’t remember who wrote it or where to find it, at the time, but now I do.
This is an old, magnificent favorite of mine. ElspethDixon is a brilliant writer in old-school Avengers comic fandom (yes, they still exist!). This is a fairy tale AU version of, obviously, the Snow Queen, in which Tony is Kai, the boy taken by the Snow Queen, and Steve is Gerda, the girl who rescues him.
Given its nature, mostly it’ll be comprehensible by movie fans, but there are a couple of characters you won’t recognize (the Scarlet Witch, the Wasp and Hank Pym/Ant Man). I don’t think it really makes that much difference, as they’re playing fairy tale roles. It just adds to the enjoyment if you recognize them.
The Snow Queen (Cap/Iron Man), by ElspethDixon