It was posted on AO3, it was an Avengers fic, and the basic plot was that Steve had followed Bucky into the army, but Steve was the one who fell from the train. He'd fallen into a lake, the moon took pity, and made Steve a winter spirit. It talks about him loving all children, but certain special favorites he'd had over the years (basically the human Avengers and Coulson). When movie events start happening, Steve draws frost pictures and tries to get everyone working together. Steve helps stop Loki, and nearly dies, wakes up in hospital bed and is shocked everyone can see him.
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