Ruin hypnotized Meliodas and Diane, who were on their way to Baste Dungeon, and made each think that the other was Ruin, resulting in them fighting. After revealing himself to Elizabeth, he starting hitting her. However, she soon understood the origin of his hypnotizing abilities, which was the bell of his staff, and managed to remove it from the staff when he hit her with it.
An angered Ruin tried to kill Elizabeth for removing his staff's bell, which was the source of his hypnotizing abilities, only for Meliodas to stop him. Whilst the Deadly Sin told Elizabeth that he accepted her resolution, Ruin, saying that the one who strikes first wins, attacked Meliodas with his staff. As Meliodas was still flying from the hit, Ruin hit him again with his staff pinning him to the ground, commenting that the former had lost his edge since he showed his back to his enemy. The Holy Knight then grabbed Meliodas from the head and lifted him, stating that he found it ridiculous that the kingdom was afraid of a small child. However, just then, Meliodas punched him, and then punched him again, sending him crashing into the walls of the Baste Dungeon, much to the surprise and shock of the guards stationed there.
Ruin, seeming to be uninjured, comments it would have been boring if Meliodas wasn't as strong as this. He, explains that Holy Knights are called so because they have magic that transcends human knowledge imbued into their bodies, and then suggests that Meliodas draw his sword, since his childlike and soft first wouldn't even scratch his armor. Ruin, seeing the young man wouldn't draw his sword, starts punching him with tremendous power, which causes the whole of Baste Dungeon to shake. Ruin thinks he crushed him beyond recognition, but Meliodas punches him in the chest, therefore breaking his armor in that area. Though Ruin then says that his armor is nothing more than shallow skin and his body, which is stronger than steel, is his true armor, Meliodas punches him again, but with so much power that his entire hand goes inside the Holy Knight's body, which makes the latter spit blood, thus defeating him. The Deadly Sin then says that Ruin couldn't have avoided his defeat, since he hurt Elizabeth, who was a person close to Meliodas, and that doing that was his sin.
After Ruin and Friesia are defeated, Meliodas and Elizabeth enter the Baste Dungeon, and encounter Ban, who had escaped from his prison before killing Jude. Meliodas' and Ban's greeting and subsequent arm wresting then destroys the Baste Dungeon despite Golgius triggering the Eternal Seal spell to trap them.