Is it worth saving Rare potions for the boss?

Yes, if the potion is a multiplier or a save. Gigantification (triple next Attack), Duplicator (next card twice) and Fairy in a Bottle (30% revive) all get better against a 400+ HP pool. Flat damage potions do not.

What is the largest heal in the file?

Fairy in a Bottle, at 30% of Max HP when it triggers, ahead of Blood Potion's 20% Max HP heal and Fruit Juice's flat +5 Max HP.

Do character potions appear on other characters?

No. The 15 character potions are locked to their pool — Ashwater, Blood Potion and Soldier's Stew are Ironclad only, and the other four characters have three each.

Which potion gives the most Energy?

Energy Potion at 2 Energy in one slot. Radiant Tincture gives 4 total but spread across four turns, which is worse on a kill turn and better across a long fight.

Slay the Spire 2 Potions — All 63 With Rarity and Effect

Slay the Spire 2 carries 63 potions, split almost perfectly: 20 Common, 20 Uncommon, 20 Rare, plus 2 Event potions and 1 Token. 46 of the 63 are shared across every character, so the pool you see is mostly the same regardless of who you pick.

The numbers are small but they are not cosmetic. Fire Potion’s 20 damage is 3.9% of Aeonglass’s 512 HP. Block Potion’s 12 Block covers the small half of an Eye Lasers turn. Fairy in a Bottle converts a lethal hit into a 30% heal.

The rarity split

Rarity	Potions	Share
Common	20	31.7%
Uncommon	20	31.7%
Rare	20	31.7%
Event	2	3.2%
Token	1	1.6%

Equal counts across the three main tiers is unusual, and it has a practical consequence: rarity tells you almost nothing about power here. A Common Energy Potion (2 Energy) is worth more on a kill turn than a Rare Entropic Brew that rolls random potions into empty slots.

Which pool a potion comes from

Pool	Potions	Examples
Shared	46	Fire Potion, Block Potion, Energy Potion
Ironclad	3	Ashwater, Blood Potion, Soldier’s Stew
Silent	3	Cunning Potion, Ghost in a Jar, Poison Potion
Defect	3	Essence of Darkness, Focus Potion, Potion of Capacity
Necrobinder	3	Bone Brew, Pot of Ghouls, Potion of Doom
Regent	3	Cosmic Concoction, King’s Courage, Star Potion
Event	2	Foul Potion, Glowwater Potion

That is 15 character-locked potions in total, 3 each for five characters. They are the ones that convert directly into that character’s engine: Bone Brew summons 15, Star Potion gives 3 Stars, Focus Potion gives 2 Focus.

The numbers that matter most

Potion	Rarity	Value	What it buys
Fire Potion	Common	20 damage	3.9% of a 512 HP boss
Block Potion	Common	12 Block	Half an Eye Lasers turn (24)
Energy Potion	Common	2 Energy	One extra 2-cost card this turn
Strength Potion	Common	2 Strength	+2 per attack for the rest of the fight
Dexterity Potion	Common	2 Dexterity	+2 Block per card, permanently
Potion of Doom	Common	33 Doom	33 damage if the target survives to trigger it
Vulnerable Potion	Common	3 Vulnerable	+50% attack damage while it lasts
Weak Potion	Common	3 Weak	Cuts incoming attack damage for 3 turns

Three attack potions in one hand — Fire (20) + Potion-Shaped Rock (15) + Explosive Ampoule (10) — is 45 damage for zero energy, which is 8.8% of the largest boss pool in the game. That is one full turn of a mid-tier deck, free.

The defensive four

Block Potion — 12 Block for 0 energy. The cheapest way to survive a spike you did not see coming.
Fortifier — triples your Block. Play it after a big block card, not before.
Ship in a Bottle — 10 Block now, 10 Block next turn, 20 total from one slot.
Fairy in a Bottle — on lethal, discard and heal to 30% of Max HP. At 80 Max HP that is a 24 HP save.

Ghost in a Jar (1 Intangible) belongs in the same conversation: one turn of taking 1 damage per hit trivialises a multi-hit turn like the Queen’s Off with Your Head (5 hits) or Aeonglass’s Eye Lasers (2 hits).

Utility that changes a turn

Potion	Effect	Why it matters
Snecko Oil	Draw 7, randomise costs	Largest draw in the file
Glowwater Potion	Exhaust hand, draw 10	Event-only; refills a dead hand
Swift Potion	Draw 3	Plain card advantage for 0 energy
Cure All	1 Energy + draw 2	Two resources in one slot
Radiant Tincture	1 Energy now, 1 for 3 turns	4 Energy total
Duplicator	Next card plays twice	Doubles a 52-damage Bury into 104
Gigantification Potion	Next Attack deals triple	Triple a 60-damage Grand Finale
Liquid Memories	Return a card, free to play	Recovers the card you needed

The multiplier potions are where the arithmetic gets silly. Bury deals 52 for 4 energy; duplicated, that is 104. Grand Finale deals 60 for 0; tripled, 180 — more than a third of Aeonglass’s 512 HP in a single card.

The full list

Every potion below links to its own page with the exact text and its pool.

Potion	Rarity	Effect
Attack Potion	Common	Choose 1 of 3 random Attack cards to add into your Hand. It’s free to play this turn.
Block Potion	Common	Gain 12 Block.
Blood Potion	Common	Heal for 20% of your Max HP.
Colorless Potion	Common	Choose 1 of 3 random Colorless cards to add into your Hand. It’s free to play this turn.
Dexterity Potion	Common	Gain 2 Dexterity.
Energy Potion	Common	Gain 2 Energy.
Explosive Ampoule	Common	Deal 10 damage to ALL enemies.
Fire Potion	Common	Deal 20 damage.
Flex Potion	Common	Gain 5 Strength. At the end of your turn, lose 5 Strength.
Focus Potion	Common	Gain 2 Focus.
Poison Potion	Common	Apply 6 Poison.
Potion of Doom	Common	Apply 33 Doom.
Power Potion	Common	Choose 1 of 3 random Power cards to add into your Hand. It’s free to play this turn.
Skill Potion	Common	Choose 1 of 3 random Skill cards to add into your Hand. It’s free to play this turn.
Speed Potion	Common	Gain 5 Dexterity. At the end of your turn, lose 5 Dexterity.
Star Potion	Common	Gain 3 Stars.
Strength Potion	Common	Gain 2 Strength.
Swift Potion	Common	Draw 3 cards.
Vulnerable Potion	Common	Apply 3 Vulnerable.
Weak Potion	Common	Apply 3 Weak.
Ashwater	Uncommon	Exhaust any number of cards in your Hand.
Blessing of the Forge	Uncommon	Upgrade all cards in your Hand for the rest of combat.
Bone Brew	Uncommon	Summon 15.
Clarity Extract	Uncommon	Draw 1 card. At the start of your next 3 turns, draw 1 additional card.
Cunning Potion	Uncommon	Add 3 Upgraded Shivs into your Hand.
Cure All	Uncommon	Gain 1 Energy. Draw 2 cards.
Duplicator	Uncommon	This turn, your next card is played an extra time.
Fortifier	Uncommon	Triple your Block.
Fysh Oil	Uncommon	Gain 1 Strength and 1 Dexterity.
Gambler’s Brew	Uncommon	Discard any number of cards, then draw that many.
Heart of Iron	Uncommon	Gain 7 Plating.
King’s Courage	Uncommon	Forge 15.
Liquid Bronze	Uncommon	Gain 3 Thorns.
Potion of Binding	Uncommon	Apply 1 Weak and 1 Vulnerable to ALL enemies.
Potion of Capacity	Uncommon	Gain 2 Orb Slots.
Powdered Demise	Uncommon	Enemy loses 9 HP at the end of each of its turns.
Radiant Tincture	Uncommon	Gain 1 Energy. Gain an additional 1 Energy at the start of your next 3 turns.
Regen Potion	Uncommon	Gain 5 Regen.
Stable Serum	Uncommon	Retain your Hand for 2 turns.
Touch of Insanity	Uncommon	Choose a card in your Hand. It is free to play this combat.
Beetle Juice	Rare	Enemy’s attacks deal 30% less damage for the next 4 turns.
Bottled Potential	Rare	Shuffle ALL your cards into your Draw Pile. Draw 5 cards.
Cosmic Concoction	Rare	Add 3 Upgraded Colorless cards into your Hand.
Distilled Chaos	Rare	Play the top 3 cards of your Draw Pile.
Droplet of Precognition	Rare	Choose a card in your Draw Pile and add it into your Hand.
Entropic Brew	Rare	Fill all your empty potion slots with random potions.
Essence of Darkness	Rare	Channel a Dark for each of your Orb Slots.
Fairy in a Bottle	Rare	When your HP would be reduced to 0, instead this potion is discarded and you heal to 30% of your Max HP.
Fruit Juice	Rare	Gain 5 Max HP.
Ghost in a Jar	Rare	Gain 1 Intangible.
Gigantification Potion	Rare	The next Attack you play deals triple damage.
Liquid Memories	Rare	Put a card from your Discard Pile into your Hand. It’s free to play this turn.
Lucky Tonic	Rare	Gain 1 Buffer.
Mazaleth’s Gift	Rare	Gain 1 Ritual.
Orobic Acid	Rare	Add a random Attack, Skill, and Power into your Hand. They’re free to play this turn.
Pot of Ghouls	Rare	Add 2 Souls into your Hand.
Shackling Potion	Rare	ALL enemies lose 7 Strength this turn.
Ship in a Bottle	Rare	Gain 10 Block. Next turn, gain 10 Block.
Snecko Oil	Rare	Draw 7 cards. Randomize the cost of cards in your Hand this turn.
Soldier’s Stew	Rare	All cards containing Strike gain 1 Replay this combat.
Foul Potion	Event	Deal 12 damage to ALL players and enemies. Can be thrown at the Merchant for 100 Gold instead.
Glowwater Potion	Event	Exhaust your Hand. Draw 10 cards.
Potion-Shaped Rock	Token	Deal 15 damage.

“Fire Potion — Deal 20 damage.” — STS2 potion data, slaythespire.wiki.gg

How to spend a potion slot

The slot is worth more than the potion. Three things decide whether a potion earns its place:

A defensive potion you never drink is a wasted slot. Block Potion only pays out if you are holding it on a 24-damage turn, and 12 Block does not save you from a 32-damage Ebb.
An offensive potion scales with your deck, a flat one does not. Gigantification tripled onto a 60-damage Grand Finale is 180; tripled onto a 6-damage Strike is 18.
Multipliers want to be played last. Fortifier triples whatever Block you already have, so it belongs after the block card, not before it.

The clearest rule: keep one defensive slot and two flexible ones. Fairy in a Bottle or Ghost in a Jar covers the turn that kills you; Fire Potion and Energy Potion cover the turn you need to finish.

Potions against the biggest HP pools

Boss	HP	Fire Potion share	Fire + Rock + Ampoule
Aeonglass	512	3.9%	8.8%
Queen	400	5.0%	11.3%
Knowledge Demon	379	5.3%	11.9%
The Insatiable	321	6.2%	14.0%
Vantom	173	11.6%	26.0%

Against Vantom, three attack potions remove a quarter of the boss. Against Aeonglass they remove less than a tenth. That is the whole reason potions feel strong early and weak late: the pools grow faster than the flat numbers.

Where to go next

The relics database covers the 296 relics that sit alongside these in your inventory, and the boss table shows which HP pools the flat numbers are actually measured against. For the cards a potion might duplicate, see the cards database, and for when to hold a slot open, deckbuilding basics.