| Spoiler warning!|
This article contains plot details from the latest books.
The Celestial Festival is a big festival at each eclipse, usually hosted at the Prism Peaks, where Orem Vacker uses his skills as a Flasher to make beautiful light formations in the sky. Elves are given marble like firecrackers that shoot up colored sparks in the air, as seen in Flashback. It is a big deal in the Elvin world, and one of their most celebrated occasions.
In Book 2: Exile, Sophie teleported in on Silveny's back at the end and circled the crowd. This addition was to help calm the Elvin people's anxiety over Sophie and Dex's kidnapping in Book 1: Keeper of the Lost Cities.
In Book 7: Flashback, Fintan tells Sophie and Fitz that the Neverseen are planning something at the Celestial Festival. The crew has an argument about whether or not to cancel the festival, and they end up going. They search through the crowds for Neverseen members, though it turns out only Lady Gisela was there. However, the Neverseen did manage to rig a broadcasting device of sorts in the Celestial Festival to reveal what was happening in live time at Everglen while Sophie, her bodyguards, and her friends faced off against multiple genetically altered trolls.