Slay the Glacial Lieutenant summoned from the Ice Stone located at Twilight's Run in northern Silithus, then return to the Earthen Ring Elder in a capital city.
We must act to preserve the balance! Time is against us.
Silithus is the Azerothian base of the Twilight Cult. In the north, they have been using new ice stones to communicate with the Tidehunter's realm. Much as I am loath to do this, the spirits will understand - you must summon one of this Ahune's lieutenants and destroy it. Perhaps this forestalling action will be enough...