Sleepweaver

From A Wheel of Time Wiki

A ter'angreal that provides the user access to Tel'aran'rhiod.  The most well known sleepweaver in the series was given to Egwene al'Vere by Verin Mathwin and was studied by Corianin Nedeal, the last Dreamer of the White Tower before Egwene..

The purpose of all sleepweavers are identical; they allow the user to enter the World of Dreams while sleeping.  They differ by shape, material, and that some require the channeling of Spirit and some require no channeling at all or allow men or those unable to channel to enter.

Sleepweavers so far revealed in the series come in the shape of a striped stone ring, an iron disc, and an amber plaque of a sleeping woman.

Elayne Trakand created several copies of various sleepweavers, but they did not work perfectly and left the user appearing misty and insubstantial in Tel'aran'rhiod.

Spoilers: Information ahead comes from The Gathering Storm; please be careful if you have not read that book yet!
Sheriam Bayanar is tasked with stealing and delivering all nineteen sleepweavers from the rebel Aes Sedai as well as demanding the deposing of Egwene by what seems to be Mesaana.  She threatened the loss of a finger or toe for each sleepweaver not obtained within a three day time limit.