The Fizz was a corrosive acid that plagued Woteba and the other worlds in the Utegetu Nebula, causing those who were exposed to it to corrode and die. After analysis of the substance by Cilghal, the Jedi determined that the Fizz was an environmental defense system featuring nanotechnology beyond anything of the Galactic Alliance, the Killik, and the Chiss. It would attack anything that appeared to harm the environment of the planets in the Nebula.
The other planets controlled by the Killiks were seeded with the Fizz at the end of the Swarm War, in an attempt to prevent them from rebuilding the Colony. The Dark Nest used this Fizz to turn Unu against the Jedi.