There are four Black Chest Demons in the video game Paper Mario: The Thousand-Year Door. To open their chest, Mario would need to find a special black key. Once he does, the Demon will emerge and will curse Mario. While the Demon assumes that the curse is bad, it actually benefits Mario in the long run by giving him special abilities. There is actually a story behind the four demons that Grifty, who sits on top of the buildings of Rogueport, tells you.
The story behind the four Black Chest Demons
Over one thousand years ago, there were four heroes who planed to stop the evil Shadow Queen. The four included a strong Toad, a Koopa Troopa, an intelligent Goomba, and a Boo. During the fight against the Queen, they were able to seal her away. Unfortunately, the demon cursed the four of them right before they sealed her away. The curse was that if they ever would let go of the Crystal Stars, a black chest would appear out of no where and lock them up for eternity. Having knowledge that the seal would not last forever, the four of them wanted these stars to be in the hands of people who needed them.
They also created the map at the start of the game. They put the map inside a chest that could only be opened by someone with a pure heart (aka Princess Peach).
- The Toad - On the account of being so tired, the Toad collapsed but was saved by a healer. The Toad knew that there wasn't much time, so he told the healer to hide it where no one could find it.
- The Koopa Troopa - The Koopa Troopa went to Keelhaul Key to hide his star, but the evil Cortez quickly snatched it from him.
- The Boo - The Boo hid his star in the Creepy Steeple.
- The Goomba - He gave his star to the Punis, which they have kept safe for the past thousand years.