Slay the Spire 2 Boss Guide
Check before every Boss room — 30 seconds to know what matters
Pre-boss deck check
Scope: main branch v0.107.1, with v0.109.0 Beta damage changes shown beside the main values.
- Survival: identify the largest telegraphed hit and whether Block, mitigation, or control covers it.
- Clock: estimate how many turns the deck needs and what mechanic becomes lethal if the fight runs long.
- Consistency: count the cards that solve the key turn, then check draw and energy access.
- Matchup: use the character plan and card recommendations as filters, not a shopping list.
Why prepared decks still lose
- Entering with enough theoretical output but no way to draw or pay for it on the danger turn.
- Spending setup resources before the boss mechanic actually demands them.
- Using a Beta move value while playing the main branch, or missing a post-patch breakpoint.
Source hierarchy
Moves and balance changes are checked against official patch notes and in-game data. Failure modes and counterplay are editorial strategy, with the applicable branch stated on each guide.
Boss checks that change card picks
Aeonglass: card-play budget
Prefer compact output, passive pressure that starts early, and defense that does not require several low-impact setup cards.
Corrupt Heart: compressed survival
Check whether the deck can block a burst turn, keep scaling online, and avoid spending life on cards that do not move a breakpoint.
Boss Prep Checklist
Use the checklist to compare the next boss against Block, damage, draw, energy, and setup risk before taking another speculative card.
12 bosses shownTap a boss for mechanics
Act 1 — The Exordium
The Guardian
Act 1 · HP: 240
Never use multi-hit attacks in Defensive Mode — Thorns will shred your HP fast.
Full guide →
Hexaghost
Act 1 · HP: 250
Do NOT drink HP potions before the fight — higher HP = harder first hit!
Full guide →
Slime Boss
Act 1 · HP: 140
Don't let Slimed cards pile up in your deck — they severely dilute your hand quality.
Full guide →
Waterfall Giant
Act 1 · HP: 240 / 250 (A8+)
Do not kill Waterfall Giant just because you can. Check the next-turn explosion first or the deathrattle can end the run.
Full guide →Act 2 — The City
The Insatiable
Act 2 · HP: 321 / 341 (A8+)
Sandpit is an instant-kill timer. If your deck is bloated or cannot draw Frantic Escape on time, normal block will not save you.
Full guide →
The Collector
Act 2 · HP: 300
Killing Torch Head buffs The Collector — think carefully before clearing minions.
Full guide →
Champ
Act 2 · HP: 440
His Block resets every turn — low-output builds can't break through. Stack Poison or save a burst turn.
Full guide →
Bronze Automaton
Act 2 · HP: 300
Kill Bronze Orbs first — ignoring them lets their sustained damage overwhelm you.
Full guide →Act 3 — The Beyond
Aeonglass
Act 3 · HP: 512 / 535 (A8+)
Every sixth card creates an unplayable Wither in hand. Each Increasing Intensity upgrades all Withers, so late cleanup alone cannot save a deck without a damage clock.
Full guide →
Awakened One
Act 3 · HP: 300
Save your potions for Phase 2! Revival puts you under immediate pressure with no time to set up.
Full guide →
Donu & Deca
Act 3 · HP: 300 / 300
Kill Deca first! Letting it keep stacking shields on Donu makes the fight infinite.
Full guide →