The Sentinels are a set of floating structures that are presumed to be some sort of control mechanism for the twelve segments of The Ring. According to the best speculation regarding the symbol of Urohringr, there are thirty-six sentinels in total; three for each segment of the ring. Where the others reside is not yet known. It is possible that (following the patterns in the symbols for Innavedr and Urohringr) that there is one each for the light side, dark side, and machine layer of the earth. However, this still remains pure speculation.

Verlax describes a time in which she flew "...past the clouds... beyond the atmosphere... surpassing the orbit of the two Sentinels still locked with this piece of Urohringr."[1] This passage seems to suggest the Sun and Moon, rather than a floating structure.

  1. Ynanhluutr ch. 167