The card game is one of the many features of Super Hero Squad Online. The game is played using a deck of 40 cards, collected by the players. Each turn, the player makes a move against the enemy player. As soon as a player has no cards left, that player loses.
Each player has a 40-card deck which serves as their health points. There's a statistic "power level" which is shared by both players, and which begins at '1', but every turn has a 50% chance of going up. The power level determines which cards can be played. The card has several values on it, including its power level and damage. For example, "Invisiburst" only needs a power level of 1, and deals 3 damage. The card also has two symbols, which represent the card's factors, such as speed, strength, animal, etc... The top symbol on the card represents what type of card the attack is, the bottom one shows the block type. Some cards have special text too, like "Here Comes the Spider-Man." On that card it says "2: Keeper. Aftershock - Whenever you do at least 2 damage with a [speed] attack, this keeper hits for 1." As long as this keeper is in play, if any "speed" factor card deals 2 or more damage, this keeper character will jump in and deal an extra 1 damage to your opponent. Mind you, keepers can be destroyed if the opponent gets a "Lucky Block".