Compass of Azaoria
The Compass of Azaoria is a mystical artifact created by an alchemist named Azaori sometime in the middle of the 10th century. It is believed that he was inspired or manipulated into its creation by an Outsider.
The purpose for the artifact is to point the way to an ancient Athanteen relic known as the Roark Skull. It has been discovered, lost, and rediscovered numerous times since its creation and it is unclear whether the artifact works for its intended purpose or not, but it is generally believed to be the only way to locate the Skull.
Of course until the modern era, it was impossible to recover the Roark Skull because it was located on the bottom of the Tyrrhenian Sea.