Baku

The is the former personal summon of Danzō Shimura.

Appearance
It is a gigantic elephantine chimera, large enough to dwarf Sasuke Uchiha's Susanoo. It is predominantly dark-orange in colour with the exception of its trunk, legs and the markings around its eyes. Its feet are striped — reminiscent of those of a tiger and it also has huge tusks, what looks like a beard, as well as long, sharp claws. It has bandages wrapped around its head and plated armour at the base of its trunk.

Abilities
In legend, the Baku is said to be able to devour dreams and nightmares, a fact that Tobi also echoed upon seeing the beast. When it opens its mouth and inhales, it can create a powerful suction force that inhales everything in its path — unaffected by the debris it inhales — while at the same time exhaling through its trunk.

Danzō uses this suction force in conjunction with his own Wind Release techniques to amplify their power. It was strong enough to immobilise Sasuke's Susanoo as well as augment Danzō's Wind Release to break through Sasuke's Susanoo's defences. This suction also has a similar effect on Fire Release techniques, which can be used against it.

Five Kage Summit
During his battle with Sasuke at the Samurai Bridge, Danzō summoned the Baku and attempted to use its powerful suction ability to destabilise Sasuke's Susanoo. He also took advantage of the suction force to increase the power of his own Wind Release: Vacuum Serial Waves technique, which was able to carve out an opening in Sasuke's Susanoo, thus allowing Danzō to attack the Uchiha head on. Using the suction to his own advantage, however, Sasuke launched a fireball into the Baku's mouth, increasing the fire's size and power and thus forcing it to retreat.

Trivia

 * A is a mythological Japanese creature said to eat dreams and nightmares. As a chimera with an elephant's trunk, a rhinoceros' eyes, an ox's tail, and a tiger's paws, they resembled somewhat the real-life tapir. After the two creatures were connected, the baku was more and more often depicted as a tapir. Modern images depicting Baku as actual chimera are rare.