The Tears of the Goddess are obtained from Tyrande Whisperwind in the night elf encampment of Hyjal Summit and is reusable. It has a 10 second cooldown and persists as long as you don't leave the instance. It will not disappear if you run back from the graveyard. Use this item on your descent after being affected by Archimonde's Air Burst ability - the effect only lasts 3 seconds, so don't use it early.
Patch 2.1.0 (2007-05-22): Added.