Monster cards come into play in the form of attacking, which can be done once per turn. Your monster cards can attack either your opponent monsters or their actual characters. Like in most other trading card games, each character and monster, including boss cards, have a set attack strength and set amount of HP with which to work with (with the character HP being changeable in the manner we discussed earlier). Turn after turn, each player takes their stabs at attacking, leveling up, etc. until one player has eliminated the other party leader.
You can use twelve sky2 Gold from your hand to level up your character on each turn, which add HP and abilities to your character roster. These abilities are found in the bottom section of each card, with each ability having a minimum level that your character must be in order to use it. Some abilities are a One time only deal, while others add different understand party members to your team. For instance, if your character is a Warrior and you place a Bowman card under it, you now have access to Bowman and Warrior abilities, as if you added a Bowman to your team.