Exonium was a fossil fuel that could be used to produce energy. The planet Rishi was rich in deposits of this mineral. The native Rishii used the mineral in food preparation. More developed cultures used the mineral as power sources for things such as sonic weapons. Exonium could be refined in a way that made it a suitable fuel for use in starships.
- Star Wars: The Old Republic: Shadow of Revan
- The Clone Wars: The Gauntlet of Death (First appearance)
- Codex Entry: Exonium (Star Wars: The Old Republic)