Forgive me, but I just had this mental image of a D&D party handling a BBEG in his fortress like a SWAT team using a negotiator.…actually mature topics--like solving problems through means other than just murdering them. It's far more mature to work out your problems through compromise and understanding than it is using violence as your first resort.
“Lord Anthraxus! This is The Troop of Steel! Come out with your hands up! Nobody wants to hurt YOU or anyone else in your keep!”
“Get stuffed”
“C’mon- it doesn’t have to be like this. Let’s talk. Help me help you. What can I do to have you come out peacefully?”
“I want a magical haversack filled with 10kGP gems and a trained riding drake! Oh yeah- a wand of magnificent feasts!”
“That’s a tall order! I’ll get my people working on it. I can get you some ale and chicken from the local tavern right now. Is that OK?”