Kokuō

The is a tailed beast sealed within Han from Iwagakure. It has been captured, extracted, and sealed by Akatsuki. In the anime, the Five-Tails is indicated to have been one of the two tailed beasts that Akatsuki captured before the start of Part II. It was then resealed back into Han during the Fourth Shinobi World War.

Background
According to Tobi, the Five-Tails first came into being in the waning days of the Sage of the Six Paths' life; to prevent the Ten-Tails' resurgence, the Sage split up its chakra and used his ability to create nine separate, monstrous constructs of living chakra, which would become known as the tailed beasts. The Five-Tails eventually fell into the possession of Iwagakure and was sealed into Han.

Appearance
The Five-Tails primarily resembles a white horse, but with a dolphin's head. It has two long horns and two short horns, which are very pointy. The ends of its horns, hooves, and tails are light brown, with some of the same-coloured spots before the brown areas of its horns and hooves. It also has red markings under its dark blue-green eyes, similar to Kimimaro's.

Abilities
Not much is known about the Five-tails, but since it is a tailed beast, it has a great amount of chakra in comparison to most shinobi and is able to use the Tailed Beast Ball. The Five-Tails can also use its horns in combat, showing enough ramming-force to even injure the Eight-Tails.

Trivia

 * According to Kishimoto's words from the second Naruto artbook, he tried to do a mix of a dolphin and a horse.