Use the Seed of Revitalization at the Earthbinder's Circle to heal the land around the crystal. Then, return to Earthbinder Galandria Nightbreeze at the Cenarion Post in Hellfire Peninsula with any information that you gain.
It must be that the evil emanations from that giant crystal are summoning the mountain giants and driving them insane.
It's too big to move, and beyond our ability to destroy, but I know a way to quell its power.
I've summoned a circle at the northwest corner of the crystal on the ridge. Take this seed to the circle and channel its powers to heal the land through the natural forces of rain, growth and insect repopulation.
Beware, <name>, I sense an external force at play here... this is not natural!