Taurus Fire

Taurus Fire, known as Ox Fire (オックス・ファイア) in Japan, is the combination of the characters Bud Bison and Taurus.

Mega Man Star Force
Taurus Fire acts as the role of the first boss MegaMan faces in the game. After Luna threatened to cut her BrotherBand with Bud for getting KOed by Geo, the FM-ian Taurus appeared before Bud and took advantage of his insecurity by promising him power to make himself useful to her. Bud agrees and the two become Taurus Fire when they next meet Geo. Taurus Fire then takes control of a truck and attempts to run over Geo, but Geo escapes and warps inside the truck.

Once inside and after navigating the truck's CompSpace, Geo discovers Luna and Zack have also been pulled in due to Taurus' power. After defeating Taurus Fire, Bud returns to normal and the rest return to the physical world, but before leaving, Geo officially names his EM form MegaMan. Once everything is explained, Bud is forgiven.

Taurus Fire is also the first boss that can be re-fought for card data. Geo receives mail from his residual data telling where to find him a short time after their initial fight.

Mega Man Star Force 2
Taurus Fire reappears as the second boss in the game. During the eating contest at Foodtopia, the stress of the competition, as well as the flames of a nearby grill unintentionally awakened Bud's memories of Taurus and caused him to transform. Omega-Xis notes that before Bud turns into Taurus Fire, some of Taurus' energy was still inside Bud, so he reawakened that power and that the Taurus Bud merged with was not the real one. It was a residual FM-ian (like Battle Network 5's Party Battle System image Data.) Fortunately, MegaMan was again able to defeat Taurus Fire.

Much like the first game, Taurus Fire is also the first that can be refought and sends Geo mail telling him where to do so. This time, his EX form is clearly visible in the Wave World instead of being located by accident.

Ryuusei no Rockman 3
Taurus Fire appears once again as a boss in the game, initiated by a Noised card from the dealers. After his defeat, Taurus somehow comes to terms with Bud, and becomes Bud's Wizard. From this point, Bud is able to Wave Change to Taurus Fire at will, and assists Geo in his quest of combatting the Dealers.