During gameplay the Overlord deck must always have at least 15 cards in it. The Overlord deck begins a campaign with the fifteen Basic 0 level cards. Further cards can be purchased using experience points as the campaign progresses. As new cards are purchased they can be added and removed from the overlord decks between quests (but not in between a quest with two encounters. The Overlord can customize which cards available to them are available in their deck as long as they always have a minimum of 15 cards in their deck at the beginning of a quest. If the Overlord draws the last card in their deck the discard pile is shuffled and turned into a new draw pile for them. The Overlord draws one card at the beginning of their turn and have no maximum hand size.