Ibuse

is a venomous salamander and Hanzō's signature summon. It was large enough for its summoner to stand on top of its head and when battling alongside Ibuse, Hanzō was powerful enough to fight, and eventually overpower all three of the Sannin. At some point it was forced into a summoning contract with Ao Jūrai through the Shireigan.

Abilities
Ibuse is able to release a Poison Mist from its mouth, which is capable of making the entirety of a victim's body numb just moments after inhalation and may eventually prove fatal, although these effects can be counteracted with the correct antidote. The poison must first be generated and then stored for a total of five minutes within Ibuse's body before it can be expelled again.

Ibuse is capable of concealing itself and navigating underground. It can then resurface beneath Hanzō's enemies and swallow them, trapping them in its mouth until they have succumbed to the fatal effects of the poison.