Combine other Soul Art cards or Elemental Orbs with a base Soul Arts card to increase its level. Depending on what you fuse the base card with will create various bonuses. For example, fusing two of the exact same cards will result in double experience. Once a Soul Art card is at maximum level, you can evolve it by combining your base card with a card of the same type but at maximum level. This results in a higher rarity card. You can also fuse cards. Take three maximum level non-evolution cards and fuse them into one strong card that can evolve.