Candy is the primary currency in the Underworld. Candy is obtained from defeating enemies and from finding candy pails throughout the overworld map. Candy can be used to purchase items and equipment from merchants and shopkeepers found throughout the game such as Jiang.
It is possible to earn an infinite amount of candy by saving at any coffin (closest one by the shed to the east of North Avenue) and then visiting Bart (Named Barnaby in the Demo) at his shop in North Avenue. For a small entry fee, Bart/Barnaby will allow the player to select one of three chests-with one of them holding a prize of candy. If you don't get the prize, simply exit to the main menu and reload the save. If you get the prize, leave Bart/Barnaby and save, then come back and repeat as needed.