Nue

At rest, Nue is little more than a formless blob of dark purple. Once it soaks up enough chakra it swells to the scale of a tailed beast and settles into a chimera's shape: a fanged monkey's head ringed by a white mane, the trunk of a tanuki, a tiger's legs, and a white serpent standing in for its tail, all lit by eyes that glow yellow. Once the Gozu Tennō is undone, its core survives as a small red dot sealed into Sumire's left palm, acting as an eye. A summoning contract lets it take solid shape again, though only as a chibi no larger than a house pet; with training it can briefly grow to about the bulk of a large jungle cat.

Though it looks like a mindless brute lured toward people steeped in dark feelings, Nue is utterly devoted to Sumire. Years in her care leave it brimming with affection for the girl it regards as a parent, so much so that it will throw itself into danger to keep her alive. In its tiny form it likes to ride on her shoulder. That protectiveness has a downside: as its strength returns, it sometimes disregards Sumire's orders and keeps attacking anything it reads as a threat to her. The creature owes its existence to Danzō, who harvested Hashirama Senju's cells, and to his devoted researcher Tanuki Shigaraki, who nursed a grudge against Konoha after Danzō's death and trained his daughter to wield the beast before passing it on to her.

Nue picks its prey by sensing the darkness in a person's heart, then possesses them and feeds their worst impulses while they remain unaware; only when the victim conquers those feelings or is knocked unconscious is it driven out. It also drains chakra to sustain and strengthen itself, and because it carries Hashirama Senju's genes it can produce a weak Wood Release that grows plants to harvest more chakra. That draining is so dangerous that Kakashi and Sai warn Naruto against using his full power near it, fearing the beast would become unstoppable. In its full-sized state it regenerates severed limbs by sprouting several smaller ones from the stump, shrugs off kunai, smashes through stone walls, teleports, and can channel its stored chakra to blow itself apart in a huge blast. It shapes chakra into tangible constructs much like chakra arms and can reinforce objects with it. Reduced to a chibi, its power falls off, but Sumire's training lets it swell into a stronger, larger form when needed.