These fiendish beings emerge from the Flux sometimes. They are chaotic evil by nature, delighting in destruction.
Further reading: https://dungeonsdragons.fandom.com/wiki/Demon
List of demons
Chronicle
Case 14e00
Referenced when Freki recognizes statue-to-demon transformation magic from a prior encounter.
Case 16e03
Two Furies—servants of cosmic justice—corrupted Oz’s monkey and attacked the agents in the Flux realm; one was destroyed, and the agents continued forward despite the supernatural threat.