The Moonwell of Purity[53, 46]
is located just east of Thunder Peak in Ashenvale. Prior to the Cataclysm it was unnamed and had only one inhabitant: Shael'dryn. Due to the destruction of the nearby forest she has since moved to Raynewood Tower. Find the 3 elementals by the road and follow the scorched ground up the right side of the map. This will lead you right to the moonwell.