How to Build a Dungeon: Book of the Demon King Vol. 6 (manga)

DUNGEON DUEL

With a queen of the elves seduced and bent to his will, and two kingdoms of men kneeling before his rule, the Demon King Aur is a force to be reckoned with. And yet an unexpected threat bursts into his dungeon: Spina, wielding powerful magic of her own. It's a battle between for survival between rival dungeon masters, colored with both love and spite! If Aur's to fulfill his dream of conquering the Holy Kingdom and the heavens themselves, he and his succubus Lila must overcome Spina's sorcerous challenge.