The comet was the most popular type of Koli ball. Ahkmou sold comet balls infected with Makuta's darkness to unsuspecting Matoran. These infected spheres brought the Matoran owners under the sway of Makuta. Takua uncovered this scheme, and he and Pohatu destroyed the infected Koli balls. The comet fell out of favor after this incident.
The corruption in the Comet balls came from Makuta's power, so it was related to antidermis.