The higher your Mercenary Rank (marked with stars), the better his or her special ability, the more damage he or she causes, and the greater the limit of his or her health. When you find duplicate mercenary cards in Chests, you Rank up that Mercenary. When you find a Mercenary part in a chest, you'll Rank up that Mercenary.

The Mercenary card shows how many parts you need to assemble a whole Mercenary or increase his or her Rank.