FOUND: Black Glass

where: AO3
Title: Black Glass
Author: floralstiel
Summary: The Winchesters live in the middle lands, away from the politics and blood shed of the north, but one day John Winchester discovers a dead body and a nearly-dead, winged child in the woods. Dean names him Cas, and they quickly discover that he is mute. Through certain events they learn that not all is as it seems when soldiers from the Empire raid their homeland, searching for mute men with wings. Cas and Dean, now grown, flee their home and attempt to escape the Empire’s clutches. Dean is captured and held by the pseudo emperor, Michael, and Cas journeys to strange and otherworldly places halfway across the world to gain power to save Dean, all the while battling others with selfish ambitions of their own.

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I only read the summary and that was maybe about a year ago, I remember the story was posted on AO3, it was a Fantasy AU, Winchesters are a neutral family or something. John goes on a hunt and stumbles across a blue-eyed angel or baby, so he and his family take the kid in, then suddenly neighboring kingdoms are gearing up for war and the Winchester family is in danger. I also recall that it was to be eventually Destial (Cas/Dean).
That's about all I can recall of the summary. If anyone has a copy of this story or knows what this story was called and where I can find it. Any help would be much appreciated, especially a copy of this fic.

thank you
sincerely
jazzy