Slay the Spire 2 builds its boss roster from 15 boss-type entries, but only 12 of them are a boss room. The other three are minions that fight beside a real boss. The HP band runs from 173 (Vantom) to 512 (Aeonglass), and the single biggest hit in the file is 45 from Test Subject #C14’s Big Pounce.
Because the acts split into two routes at Act 1, the pools are not evenly loaded: six Act 1 bosses across Overgrowth and Underdocks, three in the Hive, three in Glory.
Every boss by act
| Act | Boss | HP | Asc HP | Biggest hit |
|---|---|---|---|---|
| Act 1 — Overgrowth | Ceremonial Beast | 252 | 262 | Plow 18 (20) |
| Act 1 — Overgrowth | Kin Priest | 190 | 199 | Soul Beam 3×3 = 9 |
| Act 1 — Overgrowth | Vantom | 173 | 183 | Dismember 26 (30) |
| Act 1 — Underdocks | Lagavulin Matriarch | 222 | 233 | Slash 19 (21) |
| Act 1 — Underdocks | Soul Fysh | 211 | 221 | De-Gas 16 (17) |
| Act 1 — Underdocks | Waterfall Giant | 240 | 250 | Stomp 15 (16) |
| Act 2 — Hive | Knowledge Demon | 379 | 399 | Knowledge Overwhelming 8×3 = 24 (27) |
| Act 2 — Hive | Kaiser Crab | 408 combined | 428 | Laser 31 (35) |
| Act 2 — Hive | The Insatiable | 321 | 341 | Lunging Bite 28 (31) |
| Act 3 — Glory | Aeonglass | 512 | 535 | Ebb 26 (32) |
| Act 3 — Glory | Queen | 400 | 419 | Off with Your Head 3×5 = 15 (4×5 = 20) |
| Act 3 — Glory | Test Subject #C14 | — | — | Big Pounce 45 |
The HP order, highest to lowest
| Rank | Boss | HP |
|---|---|---|
| 1 | Aeonglass | 512 |
| 2 | Kaiser Crab (Crusher 209 + Rocket 199) | 408 |
| 3 | Queen | 400 |
| 4 | Knowledge Demon | 379 |
| 5 | The Insatiable | 321 |
| 6 | Ceremonial Beast | 252 |
| 7 | Waterfall Giant | 240 |
| 8 | Lagavulin Matriarch | 222 |
| 9 | Soul Fysh | 211 |
| 10 | Kin Priest | 190 |
| 11 | Vantom | 173 |
| 12 | Test Subject #C14 | no single pool |
The jump between Act 1 and Act 3 is not gradual. The three cheapest Act 1 bosses average 191.3 HP (Vantom 173, Kin Priest 190, Soul Fysh 211), while Aeonglass alone is 512 — just under three times Vantom’s pool. A deck that clears Act 1 on raw damage usually stalls in Glory unless it has scaling by then.
The three minion entries
Three boss-type entries never appear alone.
| Minion | HP | Asc HP | Appears with | Biggest hit |
|---|---|---|---|---|
| Kin Follower | 58–59 | 62–63 | Kin Priest | Boomerang 2×2 = 4 |
| Torch Head Amalgam | 199 | 211 | Queen | Tackle 18 (19) |
| Rocket | 199 | 209 | Crusher (Kaiser Crab) | Laser 31 (35) |
Rocket is the dangerous one: it is a 199 HP body that hits for 31 on its Laser turn, and it sits next to a 209 HP Crusher. Killing Rocket first removes 31 damage from the rotation but leaves Crusher free to stack Strength with Adapt (+2 per cast).
Torch Head Amalgam at 199 HP is nearly half the Queen’s own pool, and the Queen’s pattern reads whether it is alive. Breaking the add changes which move she picks, so the add is not optional.
Biggest hits ranked
| Move | Boss | Damage | Ascension |
|---|---|---|---|
| Big Pounce | Test Subject #C14 | 45 | 45 |
| Laser | Rocket (Kaiser Crab) | 31 | 35 |
| Dismember | Vantom | 26 | 30 |
| Ebb | Aeonglass | 26 | 32 |
| Lunging Bite | The Insatiable | 28 | 31 |
| Knowledge Overwhelming | Knowledge Demon | 24 total | 27 total |
| Slash | Lagavulin Matriarch | 19 | 21 |
| Plow | Ceremonial Beast | 18 | 20 |
| Tackle | Torch Head Amalgam | 18 | 19 |
| De-Gas | Soul Fysh | 16 | 17 |
Multi-hit moves need reading carefully. Aeonglass’s Eye Lasers is 11 twice — 22 total, 24 at Ascension — but each hit is only 11, so flat Block per hit is worth more than a single big block. Queen’s Off with Your Head is 3 five times, which is 15 total but eats 5 separate Block checks.
“Laser — Attack, 31 damage (35 at Ascension), one hit. Recharge follows and the cycle restarts.” — STS2 boss data, slaythespire.wiki.gg
Fixed cycles versus branching patterns
Nine of the twelve rooms run a fixed rotation you can memorise.
- Ceremonial Beast — Stamp → Plow, repeating. Plow gains 2 Strength each time.
- Kin Priest — Orb of Frailty → Orb of Weakness → Soul Beam → Dark Ritual, with Dark Ritual adding 2 Strength.
- Vantom — Ink Blot → Inky Lance → Dismember → Prepare, with Prepare adding 2 Strength.
- Soul Fysh — Beckon → De-Gas → Gaze → Fade → Scream. Fade grants 2 Intangible.
- Lagavulin Matriarch — opens Asleep for 3 turns behind 12 Plating, then Slash / Slash2 / Disembowel / Soul Siphon.
- Waterfall Giant — Pressurize → Stomp → Ram → Siphon → Pressure Gun → Pressure Up, with Steam Eruption building from 15.
- The Insatiable — Liquify Ground → Thrash → Lunging Bite → Salivate → Thrash Move 2.
- Aeonglass — Ebb → Eye Lasers → Increasing Intensity, with 3 Artifact at the start.
- Crusher — Thrash → Enlarging Strike → Bug Sting → Adapt → Guarded Strike, with Adapt adding 2 Strength.
The other three branch. Knowledge Demon loops Curse of Knowledge until its counter reaches 3, then switches to Slap. Queen reads whether her Amalgam has died. Test Subject #C14 reads how many times it has respawned, switching between Multi-Claw and Lacerate at 2 respawns.
What Ascension changes
| Boss | HP change | Damage change |
|---|---|---|
| Aeonglass | 512 → 535 (+23) | Ebb 26 → 32 |
| Knowledge Demon | 379 → 399 (+20) | Ponder 11 → 13 |
| The Insatiable | 321 → 341 (+20) | Lunging Bite 28 → 31 |
| Queen | 400 → 419 (+19) | Execution 15 → 18 |
| Lagavulin Matriarch | 222 → 233 (+11) | Slash 19 → 21 |
| Vantom | 173 → 183 (+10) | Dismember 26 → 30 |
| Ceremonial Beast | 252 → 262 (+10) | Plow 18 → 20 |
Aeonglass takes both the largest HP jump and a 6-point bump on its biggest hit, which is why the fight gets noticeably harder rather than just longer. Vantom’s +10 HP is minor next to Dismember going 26 → 30 — a 15.4% damage increase that will break a block plan built for the normal value.
Where to go next
The monster index covers all 115 entries with HP and act, and the Ascension page breaks down every HP and damage increase in the data. For the deck side, the cards database lists the numbers behind each answer, and deckbuilding basics explains how to build a deck that scales past 400 HP.