The only sources I can recall at the moment [aside from those mentioned already] are a few [very] brief references in the 2e City of Splendors, and Demihuman Deities has a one sentence reference to them in the entry for "Dumathoin." There was also some brief bit about them in Fall of Myth Drannor too, IIRC. And see Halaster's entry in Villains' Lorebook as well.