Infinity

Play 25 cards in a single turn - i.e. an 'infinite' combo. The principle is a thin deck where the cards you play give back the energy and card-draw they cost, so the loop never stops: cheap or 0-cost cards that draw more cards, kept afloat by an energy relic or an energy-refund card. Keep the deck as small as possible so you don't draw a dead card and stall it. Each class has its own infinite recipes (Silent draw loops, Defect Claw/All-For-One decks are popular) - build one deliberately on a run, then just keep playing until you pass 25.