Most Slay the Spire 2 runs do not die to the final boss — they die three acts earlier, to habits you do not know you have. These are the ten mistakes we see most from new players. None of the fixes require new math; they mostly require permission to do less.
Drafting mistakes
Mistake 1: taking a card from every reward. A card you cannot explain is a card that dilutes every future draw. The skip button exists for a reason — ask what problem the card solves, and if nothing comes to mind, skip. Our card reward priority guide turns this into a quick checklist.
Mistake 2: forcing a theme from floor one. Seeing one poison card and drafting poison for the next two acts is how decks end up with six poison cards and no way to survive Act 1. Let relics and rewards pick your direction, not wishful thinking.
Mistake 3: never removing cards. Shop removals feel boring next to a shiny rare, but cutting a Strike helps most decks more than any single purchase. Starter cards you keep are dead draws you get forever.
Combat mistakes
Mistake 4: ignoring intents. Every enemy announces its next move. Blocking 12 against an enemy dealing 4 is wasted energy; blocking 8 against a 24-damage hit is the run ending. Read the intent first, plan second — the monster list explains the patterns worth memorizing.
Mistake 5: overblocking when you could kill. If the fight ends this turn, block is worth nothing. New players lose health by extending fights that were already won.
Mistake 6: ending turns with energy unspent. Holding energy is sometimes right, but in STS2 leftover energy is usually a missed block, a missed kill, or a card not drawn. If this happens every turn, your deck probably needs cheaper cards.
Map and shopping mistakes
Mistake 7: always taking the greedy route. Elites are great — when your deck is ready. Before committing to an elite path, count your health, your potions, and whether a campfire sits between you and the fight. The map pathing guide gives a simple rule for when to say yes.
Mistake 8: hoarding potions. A potion used at 80% health is preventing damage; the same potion held at 5% often does nothing. Spend them the moment they change a fight, especially before elites and bosses — the potion list covers which ones are worth buying.
Mindset mistakes
Mistake 9: copying high-level builds blindly. Streamer decks assume deep game knowledge and specific relic timing. Build from your own rewards first, and use the build library as a direction, not a shopping list.
Mistake 10: blaming the RNG. Sometimes the game really did deal you garbage. But if every loss feels like bad luck, you are the common factor. Honestly retrace one loss — where did the health actually go? — and the real problem usually shows up by Act 2.