Dark Heart

The Dark Heart is an artifical organ created by Misumi of Kirigakure. Through her skill with Medical Ninjutsu as well as the Chimera Technique, she was able to obtain a sample of the Reibi in its corporeal form, and use that sample to 'corrupt' a human heart. Through this heart, the user is able to mimic the Zero-Tail's ability to create Dark Chakra.

However, the Dark Heart is not a pick-up-and-go sort of tool, like a sword or kunai, and must physically be implanted within the users body. Additionally, the user's chakra network is grafted to this new heart, which is likewise joined to their existing one. This makes the Dark Heart nearly impossible to remove without killing the person in whom it is imbued.

Additionally, the Heart functions on an emotional level, similar to the Reibi. If the user no longer possesses negative thoughts or feelings, the Heart can no longer produce Dark Chakra. To prevent this, the Heart actually affects the chemistry of the users brain, disabling them on an emotional level. The majority, if not all, of the users thoughts and feelings become dark and hateful, as the Heart severely limits the body's ability to produce endorphins.