Kind of disappointed the mid-boss is so OP. Plus, it's not really explained why the dungeon exists in the first place, how the demonic economy runs, and such. These demons show no concern for the demon king, and don't seem aware of the overlord tower (no one brings up evacuating to it as a possibility). So why were they there? And are the demons aggressors or defenders? What use is having a dungeon that doesn't bring in resources by raiding or present an obstacle to enemies by sitting on a strategic location?
I know it's supposed to be a game-like world and these are just given in the setting of a game, but once you start fleshing out the characters, you have to provide an answer for what everyone's motivations are.