The Compass was the key to locating the Thirteen Treasures of Rule. The compass lights up whenever one or more of the treasures is near, and it also is capable of emanating a beam of bluish light to pinpoint either the exact location of a treasure or the general direction that it is in. It was originally in the possession of Primus (who, likely, was the compass' creator), but after his capture by Bloth in the Sea Fields of Aymara, he gave the compass to his spiritual attendant to take to Alomar. Alomar remained the guardian of the compass, keeping it within the Abbey of Galdebar until Primus' son, Ren, came to claim it. Since then, it has remained in his possession (despite occasionally being stolen).
The compass is found in the Dragon's Maw and won after defeating Bloth.