recorded by Shadrach, Court Scribe to Amber
The Jewel of Judgement being called the Eye of the Serpent is somewhat misleading. It is called such because it allowed the Pole of Order to be recreated out of the Pole of Chaos. Although it is widely disbelieved by most scholars and historians, I have found evidence to support the Jewel being used for some magical form of observation, thus the reference to calling it an Eye.
quoted from "Esoteric Studies of the Amber Archivist's Guild"