They enslaved the snow elves. Also the last remaining Dwemer Yagrum Bagarn died during the events of morrowind. The only reason he still was alive is because he was in an oblivion realm when the dragon break happened.
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That explains why I don't know. I started with oblivion
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So did I but I had to go back and play morrowind and look up lore because I love the series so much.