Sylvion is a tower-defense type game in which attacks come down four rows and in waves. You build a deck using a unique drafting process and play cards from your hand by paying with other cards in your hand. You can play cards to the rows like fountains and trees or play animals for instant effects or to manipulate the enemy decks of cards. When all the waves have finished, you must have kept the heart of the Sylvion verdant, or else the whole forest of the Oniverse will be destroyed.

This game can be played in an introductory style, advanced mode, and includes two expansions and an appendix for further challenges and complexity.