The Four Heroes
The Wise Goomba
The Wise Goomba was one of the heroes that sealed away the Shadow Queen. She came from Boggly Woods where he used his knowledge to help get rid of all the monsters in Boggly Woods. When she and the other heroes were in dire situation, the Wise Goomba suggested using the Crystal Stars to damage the Shadow Queen. However, this doesn't work well and she suggested using the Crystal Stars to seal away the Shadow Queen. The Shadow Queen was sealed away but she used one last trick to curse all of the heroes. The Wise Goomba heads back to The Great Tree where she hid the Crystal Star in the tree. However, the Punis were being tormented by the monsters of Boggly Woods so the Wise Goomba hollowed out the tree so that the Punis can leave in safety. The Wise Goomba's soul was then sealed away.
The Stalwart Koopa
The Stalwart Koopa was a Koopa that traveled the world alone. He noticed the darkness creeping and monsters soon fought him. The Stalwart Koopa was getting overwhelmed until a brave Boo saved him with her magic. Later, during the battle with the Shadow Queen, the Stalwart Koopa manages to damage her using the Crystal Stars. However, after going with the Wise Goomba's plan, he and the other Four Heroes manage to seal away the Shadow Queen. Unfortunately, the Stalwart Koopa and the rest were cursed just as the Shadow Queen was fully sealed up. The Stalwart Koopa then heads for a southern isle to hide the Crystal Star. However, the Stalwart Koopa was tired from his journey and Cortez, the Pirate King, stole the Crystal Star from the Stalwart Koopa causing his soul to be sealed away in a black chest.
The Boo Heroine
The Boo Heroine was a Boo that was known for her cold disposition. However, after seeing the Stalwart Koopa fight so bravely, her personality changed and she helped him out using her magic. She then says that they cannot fight the demon alone and need the Goomba from Boggly Woods and the Toad from Petal Meadows. The Boo Heroine and the Stalwart Koopa joined up with the Goomba and the Toad and they all fight the Shadow Queen. Following the Wise Goomba's orders, the Boo Heroine and the others used the Crystal Stars to seal up the Shadow Queen not before the demon cursed them. The Boo Heroine then hides her Crystal Star in a steeple and her soul was sealed away near the nearby town.
The Toad Hero
The Toad Hero was a Toad from Petal Meadows. He eventually joined up with the other Heroes to fight the Shadow Queen. He and the others managed to seal away the Shadow Queen using the Crystal Stars but his and the other Heroes souls were cursed. The Toad Hero then journeys to hide his Crystal Star but he collapsed from his long journey. A nearby person heals him but the Toad Hero knows his soul will be sealed away in a black chest and gives the Crystal Star to the healer and tells him to hide it in a place where no one could find it.
Black Chests Locations
The first Black Chest is located in the area before the Thousand-Year Door of Rogueport Sewers. This contains the soul of the Wise Goomba. She then curses Mario who learns the Paper Plane ability which allows him to cross over large gaps.
The second Black Chest is located near the spiked ceiling room of Hooktail Castle. This contains the soul of the Toad Hero. He curses Mario who learns the Paper Thinness ability which allows him to turn sideways and slip through cracks in grates and cells.
The third Black Chest is located in the storage room of the Item Shop in Twilight Town. This contains the soul of the Boo Heroine. She curses Mario who learns the Paper Tube ability which allows him to roll under certain things.
The fourth and final Black Chest is located in an old, broken ship found deep in the Pirate's Grotto. This contains the soul of the Stalwart Koopa. He then curses Mario who learns the Paper Boat ability which allows him to ride over water in certain areas. Unlike the other Black Chest Demons, the Stalwart Koopa's soul doesn't appear to be evil and actually thanks Mario for allowing him to do his thing and that he feels a lot better.