All cards of the “Evolution”-set except heroes can be evolved at the “Evolution”-tab of the lab. You need two same-named cards with the same evolution-stage (specified by the stars) to evolve a new card. Click on a card and press “Evolution”-button to merge chosen cards. You will receive a same-named card with the next evolution-stage and improved characteristics. Evolution costs imperials and elemental experience.
At the “Enhance”-tab in lab you can improve your hero by spending some unnecessary cards. Choose a hero which you want to improve and move cards from the left part of screen by clicking a red arrow below the cards. Your hero will receive experience when you press “Enhance”-button. When your hero has got enough experience he’ll receive next rarity. Enhance costs imperials and elemental experience.