Drop chance after a fight

Both games start each run with a 40% chance of a potion after a fight. Each fight without a potion adds 10% to the next chance, and each fight with one removes 10%. In StS2 elite fights add another 12.5%.

In StS1, White Beast Statue makes potions drop after every fight, and a fight that already has 4 rewards gives no potion. StS2 has White Beast Statue too. For the other reward odds, see reward odds.

Rarity

Potions from fight rewards and from the Merchant roll their rarity first:

RarityChanceMerchant price
Common65%50 gold
Uncommon25%75 gold
Rare10%100 gold

The same odds and base prices apply in both games. StS2 Merchant prices vary by up to 5% either way.

StS1 sources that ignore rarity

These StS1 sources pick from all potions your character can find with equal chance, so a rare potion is as likely as a common one:

Entropic Brew and the Silent's Alchemize use the rarity roll. In combat they never give Fruit Juice.

Potions each character can find

In StS1, every character can find the same shared potions plus three of their own:

CharacterCharacter potions
IroncladBlood Potion, Elixir, Heart of Iron
SilentPoison Potion, Cunning Potion, Ghost in a Jar
DefectFocus Potion, Potion Of Capacity, Essence Of Darkness
WatcherBottled Miracle, Stance Potion, Ambrosia

Potion slots

StS1StS2
Starting slots33
Ascension penaltyA11: one fewer slotA4: one fewer slot
Potion Belt+2 slots+2 slots

StS2 also has Phial Holster, a Neow relic that adds 1 slot and 2 random potions. Sacred Bark, which doubles potion effects, is only in StS1.