Your four champions all have four challenges to complete. You need to complete them in the order they appear on the card, and once you have done your champion will perform a one-off special move that can really turn things around. These are called blessings. Make sure you read the challenges carefully, and understand what it is you're trying to do. Sometimes the state of the game will mean you can't focus on challenges for the time being, but do try and get them finished, because they really are the key to success.