So, I know theres a really good canon starting point for this: right when Hailstorm was captured. BUT I do what I want so this Au starts a little bit earlier. When Winter is about a year or two old he sneaks past the great ice cliff in hopes of finding some scavengers to study. And because I say so Wren and Sky happen to be right there. So they see a tiny Ice Dragonet only a little younger than Sky and just... adopt him. Wren's not gonna leave him to get killed by some other human, and he seems... oddly enthusiastic? about being with a human? Que canon proceeding as mostly normal. Winter's parents don't care that he disappeared and Hailstorm is never captured. Que several lovely years of Winter learning more about Scavengers than he ever could have dreamed. He's happier and less stuck up doing something he loves than he would have been growing up as a high ranked prince. Sky and Wren are equally fascinated by Icewing culture and they settle into a happy family of three. theres a slightly happier/slightly more dramatic scene in Possibility. when Sky wants to free some trapped animals and Winter helps him. Winter manages to get away without being captured and flies Wren north to try and find Sky, though like canon they arrive to late, and Winter has to rest before they can go back south. Wren makes the decision that Winter is to sparkly and eye catching to come with her on a stealth rescue mission, so instead he hides out in the nearest forest, thoroughly startling the Wingwatchers. Deathbringer is traumatized by a scary and shouty scavenger as he is in every universe . really everything proceeds as canon right up to the point where Winter and Wren hear about a school for all the tribes thats being built.
Will write arc two later but wanted to get this started and shared just imagine Baby Winter telling Wren to stop yelling because he's trying to write down his scientific observations.