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After Rico was dethroned by Fei in the tournament, the Battling Committee which was run by the Ethos Society arranged a special match for Rico and they rigged his Gear to malfunction and crash into the Kaiser's box seat. The incident lead to Rico being sentenced to execution after the Committee testified that Rico intentionally plowed Stier into grandstands in an attempt to kill the Kaiser. Rico was later rescued by Fei and along with Citan, Elly and Hammer they fled to freedom from Kislev.
In battle Stier is powerful, but it is weaker to Ether-based attacks, slow, and inaccurate. It does, however, have quality framework.
Stier relies on punches and headbutts as well as firing bullets from its vulcan chamber to unleash its deathblows. Like its pilot Rico, it can utilizes his wrestling fighting style.
- Drill War: Stier jumps to make a downward punch and firing bullets from its vulcan cannon towards its opponent. This ability will appear after Rico gains the Rico Rocket.
- Bomber Head: Stier headbutts his opponent three times and lands a powerful left uppercut to make critical damage. This ability will appear after Rico gains the Death Drive.
- Drill Driver: Stier punches its opponent and grapples it to the ground.
- Grand Slam: Stier deals three firing punches followed by a headbutt and a spinning back punch. This ability will appear after Rico gains the Banderas.
- Twister D: Stier grabs his opponent and grapples around the opponent with two giant swings before throwing it to the ground dealing more damage. This ability will appear after Rico gains the Dragon Fist.
- Hammer G: Stier goes for a punch and uppercut followed by a headbutt and grabs the opponent in mid-air and throws it to the ground.
- Mega Body: Stier lands three punches followed by left punch and a spinning back punch while he jumps in the air to send his opponent falling. This ability will appear after Rico gains the Fire Bomb.
- Sky Drive: Rico grabs his opponent and lands a piledriver to the ground dealing heavy damage. This ability will appear after Rico gains the Pile Crusher which is identical to his own move.
- Scrap: Stier goes for two punches and grabs the enemy to fire its bullets from its vulcan cannon and jumps in mid-air and lands a powerful stomp on its opponent. This ability will appear after Rico gains the Spin Strike.
- Drill Kaiser: Stier flies and using its reactor to create a deadly tornado to heavily drills his opponent in its own velocity.
- Drive Kaiser: Stier does three heavy punches followed by an uppercut as it lifts the opponent and smashes into the ground to deal critical damage.
- Iron Kaiser: Stier lands a series of punches on his opponent and it flies to summon a meteorite on both of his hands and throws the opponent in a massive damage.