12 bosses · 3,572,401 fights · updated Oct 19, 2026
Slay the Spire 2 bosses
Slay the Spire 2 has 12 bosses, three per act: Act 1 (Overgrowth or Underdocks), Act 2 (Hive) and the final bosses of Act 3 (Glory). Across 3,572,401 recorded boss fights, Aeonglass ends the most runs (24.2% of fights) and Soul Fysh the fewest (11.6%).
Slay the Spire 2 hardest boss ranking
| Boss | Act | Ends the run | Avg HP lost | Avg turns | Fights |
|---|---|---|---|---|---|
 Aeonglass | 3 · Glory | 24.2% | 73.6 | 7.33 | 203,090 |
 Test Subject | 3 · Glory | 22.8% | 75.2 | 9.44 | 310,534 |
 Knowledge Demon | 2 · Hive | 21.3% | 56.8 | 8.22 | 359,934 |
 Kaiser Crab | 2 · Hive | 19.5% | 62.9 | 8.24 | 357,415 |
 Queen | 3 · Glory | 18.7% | 64.8 | 8.56 | 306,752 |
 The Insatiable | 2 · Hive | 15.6% | 47.7 | 7.82 | 357,924 |
 Vantom | 1 · Overgrowth | 14.7% | 48.7 | 8.89 | 283,456 |
 The Kin | 1 · Overgrowth | 14.6% | 49.1 | 9.3 | 285,918 |
 Lagavulin Matriarch | 1 · Underdocks | 14.4% | 39.8 | 9.19 | 274,003 |
 Waterfall Giant | 1 · Underdocks | 13.3% | 47.2 | 10.24 | 274,122 |
 Ceremonial Beast | 1 · Overgrowth | 12.2% | 43.8 | 9 | 286,112 |
 Soul Fysh | 1 · Underdocks | 11.6% | 43.1 | 9.83 | 273,141 |
"Ends the run": share of fights against this boss that the player died in (abandoned runs not counted). From Spire Codex's community-uploaded runs, all versions, Ascension 0–10.
Act 1: Overgrowth · Slay the Spire 2 act 1 bosses
-
Vantom
- Ends the run
- 14.7%
- Avg HP lost
- 48.7
- Avg turns
- 8.89
- Fights
- 283,456
Vantom · 173 (183 on Ascension) HP
Ink Blot (7 (8) damage) · Inky Lance (6×2 (7×2) damage) · Dismember (26 (30) damage) · Prepare (buff)Hardest for the Ironclad (17.3% of fights lost).
-
The Kin
- Ends the run
- 14.6%
- Avg HP lost
- 49.1
- Avg turns
- 9.3
- Fights
- 285,918
Kin Follower · 58–59 (62–63 on Ascension) HP
Quick Slash (5 damage) · Boomerang (2×2 damage) · Power Dance (buff)Kin Priest · 190 (199 on Ascension) HP
Orb of Frailty (8 (9) damage) · Orb of Weakness (8 (9) damage) · Soul Beam (3×3 damage) · Dark Ritual (buff)Hardest for the Ironclad (16.3% of fights lost).
-
Ceremonial Beast
- Ends the run
- 12.2%
- Avg HP lost
- 43.8
- Avg turns
- 9
- Fights
- 286,112
Ceremonial Beast · 252 (262 on Ascension) HP
Stamp (buff) · Plow (18 (20) damage) · Stun (stun) · Beast Cry (debuff) · Stomp (15 (17) damage) · Crush (17 (19) damage)Hardest for the Necrobinder (15.6% of fights lost).
Act 1: Underdocks · Slay the Spire 2 act 1 bosses
-
Lagavulin Matriarch
- Ends the run
- 14.4%
- Avg HP lost
- 39.8
- Avg turns
- 9.19
- Fights
- 274,003
Lagavulin Matriarch · 222 (233 on Ascension) HP
Sleep (sleep) · Slash (19 (21) damage) · Slash2 (12 (14) damage) · Disembowel (9×2 (10×2) damage) · Soul Siphon (debuff + buff)Hardest for the Silent (19.2% of fights lost).
-
Waterfall Giant
- Ends the run
- 13.3%
- Avg HP lost
- 47.2
- Avg turns
- 10.24
- Fights
- 274,122
Waterfall Giant · 240 (250 on Ascension) HP
Pressurize (buff) · Stomp (15 (16) damage) · Ram (10 (11) damage) · Siphon (heal + buff) · Pressure Gun (attack + buff) · Pressure Up (13 (14) damage) · About to Blow (stun) · Explode (special)Hardest for the Ironclad (16.9% of fights lost).
-
Soul Fysh
- Ends the run
- 11.6%
- Avg HP lost
- 43.1
- Avg turns
- 9.83
- Fights
- 273,141
Soul Fysh · 211 (221 on Ascension) HP
Beckon (status) · De-Gas (16 (18) damage) · Gaze (7 (8) damage) · Fade (buff) · Scream (13 (15) damage)Hardest for the Ironclad (13.5% of fights lost).
Act 2: Hive
-
Knowledge Demon
- Ends the run
- 21.3%
- Avg HP lost
- 56.8
- Avg turns
- 8.22
- Fights
- 359,934
Knowledge Demon · 379 (399 on Ascension) HP
Curse of Knowledge (debuff) · Slap (17 (18) damage) · Knowledge Overwhelming (8×3 (9×3) damage) · Ponder (11 (13) damage)Hardest for the Defect (25.2% of fights lost).
-
Kaiser Crab
- Ends the run
- 19.5%
- Avg HP lost
- 62.9
- Avg turns
- 8.24
- Fights
- 357,415
Crusher · 209 (219 on Ascension) HP
Thrash (12 (14) damage) · Enlarging Strike (4 damage) · Bug Sting (6×2 (7×2) damage) · Adapt (buff) · Guarded Strike (12 (14) damage)Rocket · 199 (209 on Ascension) HP
Targeting Reticle (3 (4) damage) · Precision Beam (18 (20) damage) · Charge Up (buff) · Laser (31 (35) damage) · Recharge (sleep)Hardest for the Ironclad (22.7% of fights lost).
-
The Insatiable
- Ends the run
- 15.6%
- Avg HP lost
- 47.7
- Avg turns
- 7.82
- Fights
- 357,924
The Insatiable · 321 (341 on Ascension) HP
Liquify Ground (buff + status) · Thrash (8×2 (9×2) damage) · Thrash Move 2 (8×2 (9×2) damage) · Lunging Bite (28 (31) damage) · Salivate (buff)Hardest for the Necrobinder (17.6% of fights lost).
Act 3: Glory · Slay the Spire 2 final boss
-
Aeonglass
- Ends the run
- 24.2%
- Avg HP lost
- 73.6
- Avg turns
- 7.33
- Fights
- 203,090
Aeonglass · 512 (535 on Ascension) HP
Ebb (22 (26) damage) · Eye Lasers (11×2 (12×2) damage) · Increasing Intensity (status + buff)Hardest for the Necrobinder (26.7% of fights lost).
-
Test Subject
- Ends the run
- 22.8%
- Avg HP lost
- 75.2
- Avg turns
- 9.44
- Fights
- 310,534
Test Subject #C14 · null HP
Respawn (heal + buff) · Bite (20 (22) damage) · Skull Bash (14 (16) damage) · Multi-Claw (10 (11) damage) · Lacerate (10×3 (11×3) damage) · Big Pounce (45 damage) · Burning Growl (status + buff)Hardest for the Ironclad (23.9% of fights lost).
-
Queen
- Ends the run
- 18.7%
- Avg HP lost
- 64.8
- Avg turns
- 8.56
- Fights
- 306,752
Queen · 400 (419 on Ascension) HP
Puppet Strings (debuff) · You Are Mine (debuff) · Burn Bright for Me (buff + defend) · Off with Your Head (3×5 (4×5) damage) · Execution (15 (18) damage) · Enrage (buff)Torch Head Amalgam · 199 (211 on Ascension) HP
Strong Tackle (26 (32) damage) · Tackle 2 (26 (32) damage) · Beam (8×3 damage) · Tackle 3 (14 (16) damage) · Tackle 4 (14 (16) damage)Hardest for the Ironclad (22.0% of fights lost).
About these sts2 bosses
HP and damage are the game's own numbers; the number in brackets is the Ascension value. Fight results come from runs players uploaded through Spire Codex, so they show how a fairly experienced crowd does, not everyone. Your character matters: each boss lists who struggles with it most.
FAQ
What is the hardest boss in Slay the Spire 2?
By how often it ends a run, Aeonglass (Act 3 - Glory): 24.2% of 203,090 fights. Next: Test Subject (22.8%), Knowledge Demon (21.3%).
Who is the final boss of Slay the Spire 2?
Act 3 (Glory) has three possible final bosses: Aeonglass, Test Subject and Queen. You meet one of them, shown on the map from the start of the act.
What are the Act 1 bosses in Slay the Spire 2?
Act 1 is either Overgrowth or Underdocks. Overgrowth: Vantom, The Kin and Ceremonial Beast. Underdocks: Lagavulin Matriarch, Waterfall Giant and Soul Fysh.