Takutanuva was a merged entity formed when Takanuva and Makuta fell into a pool of energized protodermis together during their battle. The creature that emerged had a mask formed of half the Kanohi Avohkii and half the Kanohi Kraahkan. Due to the fact that Makuta's mask had been torn off just before the immersion, Takutanuva was apparently dominated by Takanuva's more benevolent personality.
Takutanuva had the powers of both light and shadow.
Takutanuva possessed all of Teridax's powers and all of Takanuva's powers. He could not combine these powers, though it might have been possible for him to use multiple powers at once.
Takutanuva was a mix of both biomechanical and energy in armor.
Takutanuva was more powerful than Teridax, but far less powerful than Mata Nui.
Takutanuva was very powerful, but not as powerful as Mata Nui because he couldn't maintain the order of the universe like Mata Nui could.
Tahtorak was stronger than Takutanuva.
The Mask of Light and Shadow was an elemental Kanohi.