Primordial Observatory

The Primordial Observatory (also known as the Sunken Vault) is a lost titan vault located underwater, northeast of the Maelstrom. The entrance is hidden within the Lightless Cavern. It contains the final three seekers known to exist on Azeroth. Azeroth's world-soul directs Magni Bronzebeard here, who in turn brings the High Priest of the Conclave with him to rescue the seekers.

Trivia

 * Battle for Azeroth added an exact copy of the Primordial Observatory beneath Alcaz Island, known as Jewelhammer's Vault.