There are powers that require you to burn a card before you can use them, make sure you choose the card carefully as it won't be available again.
It is crucial that you master the card-based magic system as your enemies are already skilled using the deck and will defeat you easily if you don't.
Keep an eye on the status bar on the right as it indicates the condition of each unit you tap on along with the status of any spells or buffs cast on them.
