Scrying was a magical skill that enabled the user to view any thing or place, provided that he or she had seen it in the past. The words used to scry were "draumr kópa," which meant, "dream stare."
When a magician scried something, an image of its current state would appear, allowing him to see what was happening to that person or object.
While extremely useful, scrying also had its limitations: as explained by Brom, if one were to attempt to view a book through scrying, and the book were not opened at a page the viewer had formerly seen, the attempt would be useless. Similarly, scrying enabled the user to view persons, but not surroundings, unless they had seen the area before.
In order to keep from being scryed wards were formed. These wards would keep an individual from being watched by enemies.
Eragon was also given a silver hammer necklace from the dwarves while on the way to Ellesméra, which prevented anyone scrying him, but drew on his own strength as the necklace is made of only metal.
Roles in the booksEdit
Oddly enough, Eragon was able to scry Arya at a dungeon - where and whom he had never seen before - during his travels with Brom. He had also seemingly scryed her in his sleep without attempting to do so. It was revealed in Eldest that Arya was searching for a familiar mind while imprisoned, and found Saphira's, so Eragon did not actually scry her. This is a theory put forward by Arya, and has not been verified by any others.
Oromis teaches Eragon a variation to scrying which not only allows the user to hear people, but also allows the user to have conversation. Eragon uses this many times in Brisingr.
The Elves utilized 'scrying mirrors' which showed a likeness of the caster, and also allowed the caster to communicate with others through the mirror - This was used when Eragon contacted Nasuada after escaping from Helgrind and being found by Arya.