A Main Deck of at least 40 cards: A Chosen Champion Unit, as well as Units, Gear, and Spells
§ 103.2 Core Rules PDF (officieel)
§ 103 To play Riftbound, a player must have a Main Deck, a Rune Deck, a Champion Legend, and a number of Battlefields determined by the Mode of Play. These are collectively referred to as a player’s deck.
