The Eight-Tailed Giant Ox (八尾の巨牛, Hachibi no Kyogyū) is a tailed beast sealed within Killer Bee of Kumogakure, and later within the brother of the 8th Raikage. Its excess Chakra has been in Anji Yamanaka for years.
The Eight-Tails resembles an ushi-oni with three long horns and a short left horn. It has an upper-body structure of a human, but has no hind-legs. Its 'tails' are really eight cephalopod arms of an octopus, and according to Killer Bee, its tails are able to eventually grow back even after they have been cut off.
Killer Bee and the Eight-Tails appear to be able to speak to each other in a much more relaxed state than Naruto Uzumaki and the Nine-Tailed Demon Fox. For example, when Naruto has a conversation with the Nine-Tails, the latter is in a cage with a special seal keeping it from taking over Naruto. As Killer Bee is one of the few people who has total control over his own tailed beast, he and the Eight-Tails can talk without such restraints, with Killer Bee even sitting on top of its muzzle. The Eight-Tails is shown to get easily annoyed with Killer Bee's crazy antics; however, that is somehow shown to be comical.
However, despite Eight-Tails' friendly relationship with Killer Bee, the Eight-Tails, like the other beasts, main goal is self preservation. For example, it was more than willing to be released and destroy Kisame Hoshigaki despite Sabu and Ponta being close by. However, behind the brutal appearance the Eight-Tails is shown to have a good analytical ability, as he told Killer Bee that if he left Ponta and Sabu and run in the opposite direction Kisame and the water will follow him and they (Sabu and Ponta) will be free.