Slay the Spire 2 Deck Building Guide — How to Build a Deck

Every Slay the Spire run is a deck building project with a boss deadline. The cards you draft decide whether floor 45 is a coronation or a funeral, and most lost runs are lost at the card reward screen, not the boss fight. This guide is the complete method: how to draft by floor, how big a deck should actually be, and the math that makes thin decks dominate. If you're brand new, pair it with the first run guide.

Rule zero: you are not building a collection

Card rewards offer three cards; the skip button is the strongest card in the game. Every card you add must do one of two jobs:

1. Fix a weakness — no Block pickup? Take Block. Can't draw? Take draw.
2. Advance your engine — the scaling plan you committed to (poison, Vulnerable stack, Stars, orb loop, summons).

A card that does neither is deck weight. This is the single biggest difference between players who clear Ascension and players who don't.

Deck size: 15–25 cards, with intent

• 15–20 cards is the sweet spot for most builds — you draw your engine every cycle and upgrades repeat every shuffle.
• 25–35 is fine for cycle decks that draw most of the deck each turn (Silent draw packages, Defect Power engines).
• 40+ is where consistency goes to die: your best card shows up once per boss.

The deck thinning guide covers removal logistics (shops first, events second) — but removal starts at the draft screen. Skipping three Strikes is cheaper than paying 75 gold to remove one later.

Draft by floor, not by wishlist

Run stage	Drafting goal
Floors 1–5	Raw playability: frontloaded damage and cheap Block. Elites don't care about your 3-card combo yet.
Floors 6–12	Pick your engine — the 1–2 cards your whole build orbits (Dominate, Noxious Fumes, Particle Wall, Glacial Frost…). Start saying no to off-plan rares.
Act 2	Fill the gaps the map exposes: AoE for multi-enemy floors, more Block for elites, draw for consistency.
Act 3	Only take cards that scale to boss length or delete boss intents. Nothing "situational" survives floor 40.

The four budgets every deck balances

1. Energy — cards must cost less than you generate. Stacks of 2-cost cards without ramp choke your turns. Energy relics and 0-cost cards (Offering, Rage) buy tempo.
2. Draw — 5 cards per turn is a budget, not a law. Battle Trance, Prophesize and Acrobatics-style effects are what let engines fire on schedule.
3. Block — 30-ish Block per turn survives Act 3 non-bosses; boss combos need a repeatable source, not one big skill.
4. Scaling — the damage you didn't start with. Strength, poison, Stars, orb loops — at least one source must be live by Act 2 or your fights outlast your HP.

Slay the Spire 2 specific deck tips

• Stars are the Regent's second energy. Regent decks balance gold-cost cards against Star generators and spenders — draft them as one economy, not two.
• Osty changes Necrobinder's block math. Her summon absorbs hits, so Necrobinder decks can draft greedier damage than other classes — but keep the Osty-protecting payoffs.
• Exhaust is a resource. Ironclad's Second Wind/Feel No Pain only work in decks that actually exhaust; don't draft exhaust payoffs into a deck with two exhaust cards.
• Curses and status cards count as weight. Event rewards like The Trial hand out curses — factor the deck-slot cost before grabbing the shiny reward.
• Co-op decks stay selfish. In multiplayer, card rewards are per-player, so build your own engine first; support cards (Plot, Tutor, Blaze) are garnish, not the meal.

A worked example: the first 10 picks

1. Pommel Strike (damage + draw, S-tier common)
2. Shrug It Off (Block that draws)
3. Twin Strike (cheap damage for floor 3)
4. Skip a second Twin Strike — you have enough floor-3 damage
5. Inflame (your scaling source)
6. Molten Fist (damage + engine payoff)
7. Skip a random rare that doesn't touch the plan
8. Uppercut (defense-in-a-card)
9. Feed (boss HP economy) — only if your HP economy is healthy
10. Bludgeon (elite delete button before Act 2)

Ten decisions, one coherent deck. That's the whole skill.

Keep reading:

• Deck Thinning — How to Remove Cards
• Ironclad Card Tier List
• Defect Card Tier List
• Beginner Tips — Mistakes to Avoid