Marvel: War of Heroes is a collectible card game featuring comic book characters from the Marvel universe. The player is an agent of S.H.I.E.L.D. whose task is to defeat super villains and recover ISO-8, crystal fragments that have been raining down on Earth from a deep space location. The game consists of missions, battles and trading cards with other players.
By performing missions the player earns experience, cash (in the form of silver) and cards. Each operation in the game consists of five missions and ends with an encounter with a super villain. Each mission works the same, as the player kills numerous defenceless bad guys before his progress bar fills up. Each attack costs energy and once the energy bar is empty the player can not progress further. He then needs to wait for it to recharge or use an energy pack that can be either earned or bought in the store. For each kill the player gains experience and when his XP bar is full he levels up. For each level up the player gets one attribute point that can be used to upgrade three different stats: energy, attack and defense. From missions the player can also earn resources and by collecting six resources of the same kind a special award is earned.
The player will get access to numerous cards each representing a super hero. They are awarded in missions or acquired through packs as well as by trading with other players. The quality of a card is based on its rarity. When fighting super villains the player uses his primary card. Cards have stats in the form of attack, defense and card XP. These stats can be raised by boosting and fusing cards and by gaining higher mastery levels. Cards also have one of three alignments: speed, bruiser or tactics. Boosting cards means sacrificing some cards to make one card stronger. Bad cards can thereby be used to enhance the best cards. Fusing cards involves combining two identical cards to produce a more powerful card.
Battles are done with other players and by winning the player can steal money and resources. Decks of up to five cards are used and the player has both an attack deck and a defense deck. A battle starts when the player selects another player to attack. The attack strength of the player will then be compared to the defense strength of his opponent and if it's higher the attacker will win. Some cards have abilities that adds extra combat power to the deck.