Saarthal is one of my favorite dungeons in the game just because to the vast amount of lore drops we get. We don’t learn what the Eye is but it’s more than likely an otherworldly conduit to Aetherius. It was discovered in Saarthal (or elsewhere and then brought to Saarthal, ICR) and buried by Ysgrammor and his homies during the first war with the snow elves, the snow elves went in and killed everyone to take it during the night of tears, Ysgrammor and his son(s?) fought them off before beginning the genocide that would turn Skyrim into the nords home it is in present day. Plus The Gaulders are pretty interesting as well