This little arc such contrived trash... There wouldn't even be a way to contain something like that slime and MCs group should have just magic barraged them all from the start. No monologuing, no giving an opportunity to escape, just dealt with. It's extremely out of character with how decisive stuff usually is here.
Damm this and the last chapter are complete garbage! They have put every single horrible contrivance they could think of into this slop. The pacing is awful, the spacial awareness is non-existent, the dialogues is excrement. Hopefully this is the exception and it gets acceptable again, but dear lord is this bad.