MutaStone

The MutaStones are, as the name implies, stones with special mutagenic properties. Two known sets exist: one kept in the Neutrino Kingdom, and another shaped into Magatama and placed on the back of an ancient Japanese mirror. The first set allows the user to turn into a "SuperMutant" version of one's self (parodying sentai series such as Sentai/Power Rangers), and the other into a "Metal Mutant" (similar to the characters of the anime Saint Seiya).

By crossing their arms whilst holding the MutaStones, the Turtles are able to combine into one being known as the Turtle Saint.