Aoda

is an inhabitant of the Ryūchi Cave and the personal summon of Sasuke Uchiha.

Background
Not much is known about Aoda's background except for the fact it became acquainted with Sasuke at some point, presumably during his training with Orochimaru.

Personality
In stark contrast to Manda, a snake of similar size to it, Aoda seems to be very mild mannered and respectful to its summoner, as shown when it addresses Sasuke with the "-sama" suffix and dutifully follows all his orders without needing to be controlled. Aoda also asked Sasuke how he could be of service the instant he was summoned.

Appearance
Aoda is a large blue snake with light green eyes and is easily comparable in size to the largest of summons. Like many snakes, Aoda possesses large infrared-sensitive receptors on its snout.

Abilities
As a snake, Aoda is extremely fast and nimble, successfully moving through an entire army of the Ten-Tails' clones, while evading all of their attacks. In the anime, it was also shown to possess a great amount of strength, easily able to strangle and toss away even the biggest of said replicas.

Ten-Tails Revival Arc
After Sasuke made his way to the main battlefield of the Fourth Shinobi World War, Aoda was summoned alongside Katsuyu, and Gamakichi by Sakura and Naruto respectively. Asking Sasuke how he could be of service, Aoda is commanded to manoeuvre through the enemy lines and get Sasuke to the main body of the Ten-Tails to which he dutifully complied. Slipping past clones of the Ten-Tails. While doing this, Sasuke manifested his Susanoo atop Aoda and used the Blaze Release: Susanoo Kagutsuchi technique on his Susanoo arrow, which he targeted the Ten-Tails with, combining it with Naruto's Wind Release: Ultra-Big Ball Rasenshuriken to create the Scorch Release: Halo Gale Jet Black Arrow Style Zero. Later, when Obito Uchiha was being controlled by Madara, Sasuke commanded Aoda to take him to Obito, only for the great snake to be grabbed by the Ten-Tails. Sasuke then told Aoda to leave as his assistance was no longer needed.

Trivia

 * Aoda's name might come from the Japanese Rat Snake (Elaphe climacophora), commonly known as.
 * Aoda's facial design seems to be based on hognosed snakes.