Yeah. All the past creatures they've "fought" are just costumes used by criminals to satisfy their own selfish ends (keeping people away from a town to harvest its gold, haunting a house so they can bravely banish the ghost and sell it to the highest bidder, continuing a crime spree of bank robbing, performing horrific acts of murder, violence and maybe even rape on the innocent people they are terryfing, ect).
I'll explain how we caught the criminals in the past (at least for the monsters that I've come up with. You guys feel free to shoot me a monster name and a picture and I'll make it into a proper villain for us) briefly so that we can look at the costumes and know the stories behind them.
Also, I'm going to shamelessly borrow from the Scooby-Doo rogue gallery with monsters such as the Giggling Green Ghost, the Black Knight, 10,000 Volt Ghost, and a few others.
As for catching the demons once they're released, I was thinking kind of like a mixture between Ghostsbusters and "13 Ghosts of Scooby-Doo" (the show this RP's demon-hunting concept is more or less based on).
From our instructor (the last surviving hero), we'll get a mystical enchantment or some kind of item like a bracelet, that allows us to interact with the demons through physical contact, despite the fact if they're ghosts or have no solid form.
The chest of Demons would be used as a sort of "Trap", opening up when a ghost is standing either on top of it or in front of it (with your character(s) holding it steady and opening the top). The Chest will only suck in the demons, not expel them. So until the chest is full again (with the exception of one spot remaining for the demon lord), the Demons cannot be released again.
