Each Golden Rush hero can be equipped with artifatcs: armor, helmets, boots, and weapons. These items enhance a hero's resist as well as its damage and other statistics. The equipment can be found on the battlefield or bought in the shop for gold or Black Gems. Both can be received as a reward after a battle.
You need gold to buy Magical (highlighted blue) and Unique (highlighted yellow) artifacts. Legendary artifacts (highlighted green) can be bought only for Black Gems. If a hero found such an artifact on the battlefield, it has to unlock it otherwise the Legendary weapon or armor will disappear after some time. However, these artifacts are really special. A full Legendary set unlocks the fourth skill for a hero!