Grimomen's last stand was in his Pitcastle where Shion arrived to save his friends. The demon planned to have Shion turn into a demon and be the lord's right-hand man, killing on command. Instead, Shion used his magic to burn Grimomen's wings off, causing the beast to change his plan - to killing Shion. Combining magic and his demonic arm, Shion felled Grimomen by punching him into the sky.
The demons of Demon World were loyal to their ruler even after the end, with warriors coming to stop Shion from escaping. Barman Drum went into detail about his love for Grimomen, telling soldiers not to mess with Shion since he had Grimomen's mark on his hand.