I believe it was a isekai/dungeon building troupe but I can’t remember anything pass that. the only scene I remember is when the MC fights an opponent general, some sort of undead, and when the MC finally beats the opponent, the opponent was going to disappear from the world and the MC had to use a special one time only (or very limited time) power that he got from some super being (god/super demon lord) to save the opponent, who gets revived and has a human form again and becomes a general for the MC. there might also be an undead dragon thrown into the mix somewhere but other than this one scene, I can’t remember anything else. Please help!
It sounds similar to Maou-sama no Machizukuri! ~Saikyou no Danjon wa Kindai Toshi~ however, I remember he used the one time power on one of his people and not the opponent.