Slay the Spire 2 Bosses — Every Boss and Elite by Act
Published 2026-09-208 min read
The full Slay the Spire 2 boss list: six Act 1 bosses, Act 2's trio, Act 3's Queen, Test Subject and Aeonglass — plus every elite by zone, with drafting tips.
Bosses are the checkpoints of every Slay the Spire 2 run: six possible Act 1 bosses, three Act 2 bosses and three Act 3 bosses, fought at the end of each act's map. Elites guard the optional reward floors between them. This list covers every boss and elite, where they appear, what beating them pays, and how Ascension changes the math. For the Act 3 finale in depth, see our Aeonglass boss guide.
How boss fights work
- Bosses appear on floor 17 (Act 1), 33 (Act 2) and 45 (Act 3) — one floor earlier in multiplayer.
- The room before every boss is always a Rest Site, so you enter the fight with a fresh upgrade or heal.
- Rewards: Act 1 and 2 bosses pay 100 gold (75 on Ascension 3+), a choice of three Rare cards, and sometimes a potion. The next act's Ancient then heals you and offers three Ancient relics.
- Ascension modifiers: A8 gives all enemies more HP, A9 more damage, and A10 pits you against two Act 3 bosses back-to-back.
Act 1 bosses (floor 17)
| Zone | Boss | Notes |
|---|---|---|
| Overgrowth | Ceremonial Beast | Ritual-damage boss; punishes long fights |
| Overgrowth | The Kin | Group-fight boss; AoE pays off |
| Overgrowth | Vantom | The Aggressive duelist; bursts on pattern turns |
| Underdocks | Waterfall Giant | Slow heavy hitter; Block-timing check |
| Underdocks | Soul Fysh | Spirit-phased boss; punishes careless burst |
| Underdocks | Lagavulin Matriarch | The classic sleep-then-shred elite, promoted; race her wake-up |
Act 1 alternates between two zones — Overgrowth and Underdocks — so you only ever see half the roster per run.
Act 2 bosses (floor 33)
| Boss | Notes |
|---|---|
| The Insatiable | Endless hunger damage ramps; kill it before the scaling wins |
| Knowledge Demon | Knowledge-based gimmick; punishes repeated identical plays |
| Kaiser Crab | Shell-Block boss; needs armor-piercing or Vulnerable stacking |
Act 3 bosses (floor 45)
| Boss | Notes |
|---|---|
| Queen | Summon-heavy royal fight; manage the adds or drown |
| Test Subject | Adapts to your deck's habits mid-fight |
| Aeonglass | The 512 HP magnifier boss — see the full Aeonglass guide |
On Ascension 10, Act 3 sends a second boss straight after the first — no rest site between them.
Elites by zone (Act 1)
| Zone | Elite | Why it hurts |
|---|---|---|
| Overgrowth | Bygone Effigy | Buffs itself while you kill statues |
| Overgrowth | Byrdonis | 81–84 HP bird elite with the egg reward; gains Strength every turn (Territorial) |
| Overgrowth | Phrog Parasite | Debuff pressure; Weak/Vulnerable pairing |
| Underdocks | Skulking Colony | Multi-body swarm fight |
| Underdocks | Phantasmal Gardener | Phased summoner |
| Underdocks | Terror Eel | Depth-charge burst damage |
Elites drop a relic — and Byrdonis is the elite that starts the Byrdonis Egg quest chain.
Drafting for bosses, zone by zone
- Before floor 17: one solid AoE card handles The Kin and swarms; single-target burst handles Vantom and Lagavulin Matriarch.
- Before floor 33: Kaiser Crab and The Insatiable check your scaling — Strength, poison, Stars or orbs must be online.
- Before floor 45: the boss list above is your shopping list — draft answers (adds management for Queen, variation for Test Subject, raw DPS for Aeonglass).
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