From WoWWiki

Lake Kel'Theril is a frozen lake in central Winterspring. The shores of the lake are home to the Ruins of Kel'Theril, which along with the lake itself is populated by many tormented spirits of the Highborne. Adventurers come here to hunt ectoplasm for their tier 0.5 armor quests.

Subzones of Winterspring
Darkwhisper Gorge • Dun Mandarr • Everlook • Frostfire Hot Springs • Frostsaber Rock • Frostwhisper Gorge • The Hidden Grove • Ice Thistle Hills • Lake Kel'Theril • Mazthoril • Moon Horror Den • Owl Wing Thicket • The Ruins of Kel'Theril • Starfall Village • Timbermaw Hold • Timbermaw Post • Winterfall Village