Riyan's Jinchūriki Forms

Riyan Uchiha is the jinchūriki of the Eight-Tailed Giant Ox, and is therefore capable of transforming into various forms that resemble his tailed beast, until he finally takes on the complete form of the Eight-Tails. So far, he has displayed a greater variety of forms than any other jinchūriki other than the beasts previous host, Killer Bee. Unlike Naruto and Gaara, he has full control of the Eight-Tails and his transformations, however he seems very wary of transforming into the beast or using it's chakra, preferring his Uchiha Kekkai Genkai powers to the power of the Eight-Tails.

Version 1
Using his own chakra, Riyan can freely and quickly form a demon cloak that surrounds his body. Once activated, his canine teeth and nails grow long and sharp. The cloak itself gives Riyan paws of chakra around his hands and horns on his head. He can also create an additional set of horns on his forearms to use for his own version of the Lariat attack.

He enters a three-tailed form during his fight with Kitsunekamen, and one, four, seven, and eight-tailed transformations at different points during his battle with Kurisu Taizen. Like Naruto's first three transformations, these tails are transparent with bubbles of chakra forming on the surface. Other than an incremental increase in Riyan's strength and speed, there are no obvious differences between the number of tails.

Version 2
By tapping into the Eight-Tails' chakra reserves, Riyan can enter "version 2" transformations. As stated by Sabu when he witnessed the previous host's transformation, this is done by forming the chakra into a human shape. These transformations are meant to give him an edge in battle without completely releasing the Eight Tails, as that would endanger anyone around him.

The version 2 chakra cloak is much darker than version 1 (similar to Naruto's four-tailed form and upwards). Hooves form around his feet, the horns on his head elongate, and a final "chin horn" resembling that of the Eight-tails appears. While in this form Riyan becomes more muscular, and if necessary can create chakra bones, such as a bull's skull, to increase the strength of his attacks.