Sylvion is a game where you have to defend yourself. You build a deck and play cards from your hand by paying with other cards in your hand. You can play cards to the rows in front of you, such as fountains and trees or you can play animals for immediate effects or to manipulate the enemy decks. When all attacks have ended, you must have kept Sylvion's heart green, otherwise the entire forest of the Oniverse will be destroyed.