Levels can contain up to six different chests from which you can obtain loot.
Silver chests contain equipment and occasionally diamonds.
Gold chests contain a gold star, which is needed if you want to complete the levels with three gold stars. No additional value is given for this accomplishment.
Special golden chest:
Some levels contain special golden chests that require up to 35 gems to open and will give you a stronger item than silver chests do at that level.
These chests appear like slightly bigger silver chests, but turn into monsters as soon as you try to open them.
These chests try to run away when you approach them.