The Forty-Third Floor Guardian was the unnamed Guardian of the 43rd Floor. It is the only Guardian that is dead, leaving the 43rd Floor without a Ruler and its shinsoo without a master.
At some point, Enryu entered the Tower and annihilated several fanatics of King Zahard stationed on the 43rd Floor. Because of this, the 43rd Floor Guardian appeared before Enryu. Enraged, the Guardian fought against Enryu by changing its forms. The immortal creature, an existence that was thought to be invincible, was not capable of stopping Enryu, as its flesh and blood were torn and scattered, powerless in the face of Enryu’s attacks. Even its extraordinary ability to freely use the floor’s shinsoo was to no avail against the Irregular. During the battle, mountains and seas and buildings of the 43rd Floor were destroyed, causing the land to become dyed in red. In the aftermath, the Guardian was defeated and died, causing the shinsoo of the 43rd Floor to lose its master.