The beast was unbound in recent times by three of the present four Legendary Heroes, Motoyasu, Itsuki, and Ren, who believed themselves capable of defeating it invidually. When its rampage began, the beast and its familiars more or less ignored the heroes, who didn't even seem to be able to phase it, and pressed on. During its early rampage its overwhelming might caused Motoyasu and Itsuki's teammates to abandone them, while Ren and his party fought it until only Ren was left alive.
With the other three heroes MIA and the Seven Star Heroes a fair distance away, the Shield Hero, Naofumi, is left to find a way to defeat it. Allying himself with the Queen of Melromark and several other country leaders to form an allied force, Naofumi battles the turtle once to assess its power, then a second time to buy his allies the time they need to infiltrait its body.
After rejoining his allies and reaching the beast's heart, Naofumi and his group succeed in sealing it, only for it to immediately break the seal and continue its rampage, forcing them to retreat. Realising Keichi left behind hints on how to destroy the monster in Japanese, Naofumi's party and the knights assemble the ancient gliphs upon its back so that he can read them. With this, Naofumi theorises that the beast will only die if both the head and heart are taken out, and proceeds to destroy the head with Blutopher while Raphtalia and Firo destroy the heart. The beast dies mere moments before it could kill anyone in Melromark's Castle Town.
It was later harvested for parts, and perishable items such as its flesh were disposed off. Being too massive to actually bother moving the beast out of the way, the Queen decides it will simply be better to leave its mountainous shell where it came to lay.