The language used to command magic. It is impossible to lie while speaking it, and spells cast using it are bound entirely by the literal or intended meaning of the words.

A colossal, sentient tree in Ellesméra. It was formed when an ancient elven woman, Linnëa, sung her consciousness into a tree after a tragic heartbreak. 5. Linguistic Glossary (The Ancient Language)

The language of the elves. Magic users must speak it to cast spells. Because it is impossible to lie in the Ancient Language, it is also used for making unbreakable oaths.

He turned back to the index. Under Eragon, as a word , there was a new entry:

Christopher Paolini’s Inheritance Cycle began with Eragon in 2002, launching readers into the vast, detailed world of Alagaësia. The series follows a young farm boy who discovers a dragon egg, reviving the legendary Dragon Riders. This index covers the core elements from Eragon , Eldest , Brisingr , and Inheritance . 1. Major Characters of the Inheritance Cycle