Thyralabe is a unique artifact appearing in <aed2> and later in Eremidia An Empty Tome. It serves a purpose as a navigation tool in The Rift, primarily used to locate Great Library and its numerous hidden “shortcuts” to reach the hub of all knowledge in The Rift.

The name “Thyralabe” comes from the words “θύρα” (“thyra”, lit. door) and “λαμβάνω” (“lamvano”, lit. to take). Literally, the artifact's name means “to take the door”, implying its primary function for reaching the Great Library's entrance doors.

Thyralabe is a construction made from several brass pieces assembled together perfectly, comprising a disc shape roughly in size of an adult human's open palm hand. It resembles an astrolabe in many perspectives, with some exceptions:

• Several tiny, flat gemstones studded on the limb of the instrument, which each of the gemstones can freely move over the groove of the ring;
• The rule's shape is slightly bent sideways;
• The plates used on the instrument projects several spheres instead of one;
• Its rete points out several known “major beacons” instead of stars, each represents known Rift regions; and
• On its alidade, there is a tiny lens on one of its side, in which lens engraved several guidelines visible by the user's eye by taking a peek on the lens from the other side of the ruler.

The plates used in the Thyralabe are commonly known among Riftwalkers as “skyglyph”, and are unique in each major Rift regions due to its relative position upon the Lux Primus.