The inkwell

Cards cost ink, the number in the hexagon at the top left. You make ink by putting cards from your hand facedown into your inkwell.

Two rules: you may ink only one card per turn, and only cards with the inkwell symbol, the golden swirl around the cost. Cards without it can't be inked.

Each card in your inkwell pays for 1 ink per turn. Spending ink exerts it, and it all readies again on your next turn.