The Sacred Flame

Bring the filled phial to Rau Cliffrunner at the Freewind Post in southeastern Thousand Needles. You can get to the Thousand Needles by taking the Great Lift at the southern edge of the Barrens.

I wouldn't be surprised if you can help us out further.

I don't suppose you've been sent by Zangen, hm?

Hm, yes, this phial of water will serve our purposes perfectly. Because of the shared ancestry of the dryads and the centaurs, the water of the moonwells will enable us to breach the protection of the eternal flame surrounding the centaur relic.