I did find reference to the Kingdom of The Thousand Dawns on pages 16 & 17 of Emer II under the Palian Archipelago and Palia sections. In 3000 - 4000 they were listed as, along with Erlin of the Silver Forest, being in conflict with Dark Powers. No mention of who the dark powers were, and that was all I found in Emer II.
Master Atlas v4 mentions them a number of times, and specifically calls out problems with the Vulth Horde, but that was close to the end of the Second Era. Ulya Shek is really only mentioned in connection with Jenkyna in V4 iirc. I don't recall anything more expansive on her in any of the other books, but I don't remember everything in them either.
Vulth Horde