Mutant Turtles: Choujin Densetsu-hen

The Teenage Mutant Ninja Turtles obtain Mutastones from Crys-Mu, a spirit of light, which allow them to temporarily boost their abilities as Super Turtles for three minutes. At the same time, Shredder and his henchmen Bebop and Rocksteady find the Dark Mutastone, transforming them into more powerful versions: Devil Shredder, Supermutant Bebop, and Supermutant Rocksteady. The Turtles have an additional advantage: they can merge into a single, more powerful entity known as Turtle Saint.