The third book in the Inheritance Cycle. The inpronouncable name means "fire", which is associated with the first spell that Eragon learns. However most readers have attributed it to the feeling of their brains being lit on fire due to the mind-boggling complexities of prose.
“Nasuada hoped he would soon recover. If he did not, she would ask Eragon or Angela, or perhaps the two of them together, to attend to Garven. Until such time as his condition improved, she decided that he should no longer serve as an active member of the Nighthawks; Jormundur would give him something simple to do, so she would not suffer guilt at causing his any further injury, and he might at least have the pleasure of enjoying whatever visions his contact with the elves had left him with.Bitter at her loss, and furious with herself, with the elves, and with Galbatorix and the Empire for making such a sacrifice necessary, she had difficulty maintaining a soft tongue and good manners.” Quote from Brisingr
An attempt by scholars to re-introduce the joy of reading the Thesaurus to the younger generation by attatching to it characters and the occasional event. The book cover claims it was written by Christopher Paolini, but we know better.
"I have a new name for pain."
"Layer upon layer of pregnant clouds blanketed Palancar Valley, clinging to the mountains with tenacious arms and filling the air with heavy, cold mist. From inside, Roran watched as cords of gray water pelted the trees with their frothing leaves, muddied the trench around Carvahall, and scrabbled with blunt fingers against the thatched roofs and eaves as the clouds disgorged their load. Everything was streaked, blurred, and hidden behind the torrent’s inexorable streamers," An example of how Eldest appropriated the Thesaurus to describe rain
"The sandstone around her nose shimmered like gilded dew, turning clear with dancing silver highlights. Eragon watched in wonder as tendrils of white diamond twisted over the tomb’ surface in a web of priceless filigree. Sparkling shadows were cast on the ground, reflecting splashes of brilliant colors that shifted dazzlingly as the sandstone continued to change"