Acid Pills were pills composed of a horribly corrosive form of Acid. When consumed (Or, presumably, exposed to any moisture) they convert into acid. Consuming one was fatal. Liit found some of these during his imprisonment on the Exon, and used them in self-defense against the Space-Balls, tricking or forcing them into consuming some of the pills, which would then destroy them from the inside. The Acid Space-Ball was created in this manner. He survived the influence of the acid pill, and became perhaps more deadly, due to his acidic nature.