The sporocystian toxin is an energy-based poison developed by Tuvok and The Doctor, working from the remains of the Caretaker. The toxin is designed to break down a critical enzyme in the Nacene cellular structure, causing temporary paralysis; while Tuvok recognised that the Caretaker had been essentially benevolent, faced with the possibility of encountering another member of the Caretaker's race, he considered it prudent to develop a means of defending themselves.

In 2372, Captain Kathryn Janeway deployed the toxin against Suspiria when she threatened USS Voyager, forcing her off the ship. (VOY: "Cold Fire")