@Mizuho9000
Oh, I actually thought about how Skelly-chan could be the boss but I wasn't sure I wanted to consider that she needed to be defeated. I would have expected that a stampede would occur with the dungeon boss' will and I don't think she wants that. Is she even still a monster? It seemed to me that she probably was a strong adventurer who reached the last level but was defeated by the boss (the black shadow thing absorbed by MC's staff) and then used as a puppet. I guess we'll learn more about her later.
Actually now that I'm saying it, if the dungeon boss is the black mist thing, and it was absorbed by MC's staff, was it ever defeated? Maybe MC can just wave his staff and guide the monsters back in the dungeon now. It might be that because MC is incredibly excited right now he is unintentionally triggering the stampede.
It still makes no sense where the monsters are coming from.