So here's my idea. I like the cute characters in Monster House and Grabbed by the Ghoulies. Also the music from the Nightmare section of Pinball Dreams is another inspiration. https://www.youtube.com/watch?v=_lMC-vxcF4c
As the monster you own the house ( think Dungeon Keeper ). At first a lone kid enters looking for the treasure. Using pathfinding the kid will move through the house to collect the treasure then escape. If any loot is taken the level is lost. You have a range of ways to stop this from happening. Scaring, traps, blocks (to delay - lock the door), divert (open a door and offer something better than the treasure to lure them) and attacks. You are corporeal (ghost) for most of the time and move things around, but you can manifest in physical form to do physical attacks only when you have sapped enough fear from the kid. Rinse and repeat for each new level, but the difficultly is introduced by adding more kids at the same time, more treasure to lose (any 1 loss of treasure is a fail) and any kids who survived a previous level gets a +1 against fear next time, making them harder to scare.
