The Sun Elves of Sol'Sylvaine

From the introduction: High atop the treetops of the deepest unexplored parts of Redsaw forest lies the ancient city of Sol'Sylvaine. The reclusive elves that built the city millennia ago live there in balance with nature practicing the highest forms of magic. Lightweavers of old have hidden the city from the prying eyes of the lesser races, but most locals know not to venture deep in the forest because the elves do not take kindly to trespassers.