The Mimir

The mimir, also called the Well of Knowledge or the Speaking Skull, is a minor magical item common to The Outlands. This device gives answers to spoken questions, as long as they have been recorded by the mimir's creator. Mimirs can shed light on any number of subjects, but the most common type gives a brief tour of the Outlands and its gate-towns.
Mimir come in many forms, disks, cubes, leaves, stars, sunflowers, and plenty of other shapes, but a humanoid skull is by far the most common variant. They are all made of an unknown silvery metal that shines and reflects light with a rainbow hue. Covering the object will be fine lines and patterns all over the surface.
Should the owner ask it a question, it will click for a few seconds before speaking its answer in an instructive, conversational tone. A mimir can also answer where on the Outlands its owner stands, but only in a general sense. It cannot be used to give exact distances or directions, but it will say from which outward ring from the spire he's standing in. Mimir only function on the Outer Planes, if brought to any others it will simply babble incoherently.
These devices rarely get lost as they float naturally behind their owners just like ioun stones. This makes it easy to spot a Prime since they would be the one with a skull bouncing behind them. For this reason many folk keep their mimir in boxes or sacks.
Nobody quite knows where the Mimir come from, but they are commonly for sale (~2000gp) in the gate-towns and Sigil.