B’t X, a mechanical AI warrior forged by the Machine Empire as one of its ultimate combat machines, was discarded into a scrapyard after falling out of favor. Its dormant systems reignited when Teppei Takamiya’s blood spilled onto its frame during a skirmish with Empire forces, forging an uneasy alliance marked by clashes between X’s ingrained distrust of humans and Teppei’s headstrong impulsivity.

Designed with a sleek avian-inspired form featuring wings and talons, X wields lethal capabilities including supersonic flight and plasma-based weaponry. Its power hinges on a symbiotic bond with its human partner, demanding mutual trust and synchronization to unleash its full potential. Their initial partnership fractured over opposing tactics—X’s calculated self-preservation clashing against Teppei’s reckless resolve.

A turning point emerged when X shielded Teppei at the cost of its own destruction during a critical battle. Revived by the Spiritual Guardian Hokuto and the B’t Max, X returned with upgraded systems and a fortified bond with Teppei, erasing past discord to function as a unified force against the Empire.

In later campaigns, X became instrumental in thwarting Raphael, the Empire’s rogue superweapon bent on annihilation. Their synergy, supported by allies like the reformed Spiritual Guardians, traced X’s transformation from a detached war machine to a guardian committed to humanity’s survival, embodying themes of loyalty and self-redemption.

Beyond direct alliances, X’s former prominence within the Empire and confrontations with rival B’ts like Shadow and Rafaello cemented its role as a bridge between mechanized oppression and organic resistance. Its actions consistently affirmed its dual identity: a protector bonded to Teppei and a living challenge to the Empire’s tyranny.