Stone of the Tides

is a quest item only lootable by players on the quest. This is a powerful magical artifact that was once used by the might Gurubashi troll empire. It allows the user to control all sorts of water and to summon water elementals. However, it also places a curse on the user which causes them to slowly fade out of existence.

Source
drops from Gazban the goblin wizard. To summon Gazban, you must be on the quest and use  to destroy the Altar of the Tides. The altar is found deep underwater in Stranglethorn Vale, in the area known as the Vile Reef.

As a Quest Objective

 * - from Catelyn the Blade at the inn in Booty Bay, in Stranglethorn Vale
 * Required:
 * Stone of the Tides
 * Catelyn's Blade (provided)