Energy

Energy is the primary resource used to play cards in Slay the Spire. Each turn, players begin with 3 Energy by default (modified by certain relics and cards), and any Energy not spent is lost at the end of the turn. Playing a card costs the amount shown in the top-left corner of the card, and cards cannot be played if you lack sufficient Energy.

Several mechanics interact with Energy. Some relics increase the per-turn Energy supply, such as Sozu (which grants +1 Energy but prevents potions). Cards like Spot Weakness and Feel No Pain do not directly generate Energy, but X-Cost cards spend all remaining Energy for scaling effects. Managing Energy efficiently — ensuring you play the highest-impact cards each turn — is a core skill in the game.