Board Thread:Lore Discussion/@comment-26323732-20150424080355/@comment-1738746-20150424082126

Lots of people have lots of different theories. But canon-wise, there is no lore provided on it and as far as explained, there was no priest associated with it. Most people agree on the theory that the mask was made for the Dragonborn considering the priests all knew Alduin was going to return. The fact that the mask has no lore, no mention, and no usage despite the thousands of years further supports it was meant to be found by the Dragonborn or by someone else further in the future and the DB simply stumbled on it.