I got a few days late of a start on this, but I'm glad to have managed to make something for this, and in RPG Maker no less.
You have a house and adventurers come in to explore and take things, because that's par for the course. You decide to take action and contact someone in construction. You now control a dungeon and adventurers come in to try to explore and take things, but now you can defeat them and ransom them back for money. As they fall, they return with new strength.
I would have liked to have more NPC dialogue and responses based on personality and how many times they'd already done this, as well as add other criteria/effects such as traps influencing NPC evolution, but I just flatly ran out of time. Setting up the NPC AI and making sure all 21 of them felt different and interesting was enough of a task in and of itself, let alone the battles and trap/bonus systems.
Since you technically control the NPCs to move them through the dungeon I'm safe from the patent as they aren't technically a "non-playable character", even though they battle automatically and you can't influence their behavior outside of how you manipulate the world around them. I may add more to this if people think it's interesting enough to do.