OVA
Description
Crys-Mu is a spirit of light bound within the Muta Stone, originating from the lost Muta Kingdom's subterranean temple beneath the Neutron Kingdom. Embodying purity and order, she serves as guardian of the Light Mutastones of Courage. Her existence is intrinsically linked to the ancient Mutastones, potent mutagenic crystals granting transformative powers.

Imprisoned within the temple for an unknown duration, she awaited prophesied heroes destined to wield the Mutastones. Recognizing the Teenage Mutant Ninja Turtles as those chosen warriors upon their arrival, she entrusted them with the Light Mutastones. This act granted the Turtles "Super Mutation," a temporary transformation into enhanced "Super Turtles" lasting three minutes. She further revealed that uniting all four Super Turtles could forge the "Turtle Saint," an ultimate fusion form enduring only 100 seconds.

Crys-Mu acts as guide and mentor to the Turtles, instructing them in utilizing their new Mutastone-derived abilities and special techniques. Her primary purpose is countering the threat posed by her counterpart, Dark Mu, the demonic spirit of the Dark Mutastone of Greed. Dark Mu embodies chaos and destruction, feeding on negative energy and planetary phenomena like dying stars. Crys-Mu and Dark Mu share a sibling-like bond, representing opposing forces of light and darkness within the Mutastones' mythology.

When Krang and Shredder awaken Dark Mu using the Dark Mutastone, her destructive power threatens Earth. To empower the Turtles against this threat, Crys-Mu facilitates their fusion into the Turtle Saint. Confronted by Dark Mu's overwhelming power, Crys-Mu makes a critical decision during the final battle. She sacrifices herself by physically restraining Dark Mu, enabling the Turtle Saint to deliver a simultaneous attack that destroys both spirits. This act of self-sacrifice neutralizes the immediate threat and severs the Mutastones' connection, stripping both the Turtles and their foes of the transformation abilities she bestowed.

Her legacy is defined as the initial bestower of the Super Mutation powers and her ultimate sacrifice to preserve cosmic balance.