The Thrall-Noldorin are those Elves of the Noldor who have become slaves of Morgoth. In the earlier conceptions of what would become The Silmarillion, all Elven realms of Beleriand were destroyed much earlier than in the final work, and virtually all the Noldor were enslaved by Morgoth as his thralls, working in the mines of Angband doing Morgoth's work. The only free Noldor were escaped thralls or lucky refugees, who were mistrusted by the Sindar.