Eldunarí
From The Inheritance Encyclopedia
The Eldunari (Heart of Hearts) is a gem-shaped organ near a dragon's throat which dragons could store their soul into. All dragons knew of the heart of hearts but did not consider it much importance until the revelation was made upon them once the Riders deemed it fit that they had enough experience to handle the knowledge. Some dragons extracted their Eldunari for mere convenience so they can be in constant communication with their partner and lend their strength whenever he/she needed it. Once it is extracted, it can never be taken back. The Eldunari will live forever until someone breaks it for them or they have an impulse to do magic and destroy it themselves. Not many dragons can destroy their own Eldunari but it is not unheard of. Before the fall, the wild dragons of old stored all their Eldunari in "Du Fells Nangoroth." They allowed the Riders to watch over them.
Once the dragon's physical being dies, it sometimes goes into its heart of hearts. In this position, it can communicate through its mind but has no body. It lives through its soul. On rare occurrences, the dragons can use magic. When a dragon served it's Rider while it's body was dead, but was in it's Eldunari, the relationship was called Indlvarn.
Eldunari are the source of Galbatorix's power. By stealing hundreds (maybe thousands) of Eldunari, he tortured them and slowly broke their minds and binded them so that they would serve him. He spent the majority of 40 years (of which he never left his castle) trying to crack them. The larger the Eldunari, the more energy it can hold before becoming saturated.
It is not specified that Galbatorix took all the Eldunari from Du Fells Nangoroth since his education was incomplete and didn't know of them at the time he betrayed the riders, however it was stated by Oromis that all Eldunari were accounted for when Eragon asked him about them Brisingr.
[edit] Theories
It is possible that Eragon try and find the Eldunari in Du Fells Nangoroth. Trying to cut off Galbatorix from the Eldunari may be one of the only ways Eragon can beat him. Eragon will try to find the Eldunari of Bid'Daum or Vrael's dragon. It is a very possible theory that Vrael's dragon was named Kuthian and the Rock of Kuthian will be his Eldunari.
See also: Dragons
