Hiru

Personality
The Reibi is evil by nature, constantly trying to bring fear and misery to host and opponent alike. The leech feeds off these negative emotions to create Dark Chakra, the source of its power.

Appearance
The Zero-Tails primarily resembles a dark purple leech with a serpent-like body. On its face, it wears a Noh mask that has the kanji for "zero" (零, rei) and five red hair-like strands sprouting from it. It also has a mouth that can open very wide that contains large molars.

Abilities
Like Kurama, the Zero-Tails has the ability to sense negative emotions, to which it uses to seek out and possess anyone who is emotionally unstable. Soon afterwards, it begins to feed upon the darkness within one's heart and allows the spirit to create dark chakra (闇のチャクラ, yami no chakura). The dark chakra produced by the Zero-Tails grants its host a great source of power, giving them access to high-level techniques without even using hand seals while negating any potential drawbacks those techniques may otherwise bring, as well as powering up the entire floating fortress. It appears to have the ability to read the hearts of others. The Zero-Tails is also able to instantly reattach itself whenever it lost a part of its body, even its head.