Shinigami

The Shinigami is a translucent, gaunt spectre with a demonic visage. It is much larger than an average human, possessing long, shaggy, white hair, from which two red horns protrude, as well as purple-hued skin. It is draped in a large white kimono and carries a set of prayer beads. When not using it, the Shinigami is almost always seen with a tantō in its mouth. When removed, however, its mouth is revealed to be full of sharp, jagged teeth, and a very long, almost serpentine tongue. When sealing a target, a series of cursed seals spread across its arms.

The Shinigami was first summoned by Minato Namikaze, the Fourth Hokage, as a last resort, with the intention of sealing the Nine-Tailed Demon Fox into his infant son. However, he wasn't able to seal the entirety of Kurama's chakra into the infant, due to the immense amount of chakra the beast possessed being too much for the newborn. Using the Shinigami, Minato was able to seal the yin half of the tailed beast within himself, before going on to use another sealing method to seal the yang half of the fox within his son.