Bring 8 Wavefront Medallions to Geranis Whitemorn in the Ghostlands.
Every year we, the denizens of Suncrown Village, would take part in a ritual to keep the different aspects of nature under our control. Dominion over the element of water was symbolized by the summoning and enslavement of an elemental named Aquantion. Through a wicked perversion of our magic, the scoundrel broke his bonds and enslaved us instead!
We wore medallions shaped like waves during the ritual. Seek them at the bottom of the lake; we'll need them to free my compatriots' spirits!