When opened the box presents you with a puzzle asking which shape contains which number or which number is in which shape. Upon completing the puzzle the player receives coins, gems (Sapphire, Emerald, Ruby, or Diamond) or a half key. Ignoring the strange box results in spawning of even more strange boxes. The strange box only stacks when there are no available spaces for it to spawn another box into. Casting High or Low Alchemy on the box, dropping it, or banking it also causes another box to spawn.
If the player receives the strange box when they had a full inventory, the Mysterious Old Man instead teleported them to a maze.