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SLAY2

Probability Observatory

Exact odds, with the arithmetic in plain sight

Every number below is computed in exact rational arithmetic from rules checked against the game’s own data and the published tables. Tap “exact” beside any percentage to see the fraction behind it. Where a relic or mode changes the rules, the calculator says what it does not model.

Is this your profile’s first-ever run?
STS2 main v0.107.1Ascension not set · A0 assumed

Card rewards

Rarity odds and the hidden pity counter

ExactA0 assumed
Where do the cards come from?
How much do you know about your counter?

0 at the start of a run and right after a rare. Capped at 45. Every card in a pack counts, including the ones after a rare in the same pack.

Normally 3; some relics change it.

Chance of at least one rare · normal fight, 3 cards

0%

First card in the pack

  • Rare0%
  • Uncommon35%
  • Common65%

How many rares will the pack hold?

100.0%0 rares1 rare2 rares3 rares

Expected rares: 0.000

Exactsts2-main-0.107.1How this is calculated

Rules: CARD-1, CARD-2, CARD-3, CARD-4, CARD-5, CARD-6, CARD-7, CARD-10, UPG-1 · evidence classes E1, E3, E4, E6

Assumptions

  • Each card is rolled one at a time; a rare resets the hidden counter to −5 points and every other card adds +1 point (A7: +0.5), capped at +40.
  • A run starts at −5 points, so history that begins at the first reward is fully determined by what you saw.
  • Boss packs are three rares and also reset the counter; shop cards read the counter without moving it; events and relic packs use fixed base odds.
  • Ascension not confirmed: A0 base rates are assumed.
  • The game compares float32 thresholds; this engine uses ideal decimal arithmetic (difference below 1e-6).

Not modelled

  • Relic and event hooks that change odds (e.g. Prayer Wheel, White Star, Molten Egg, Dingy Rug).
  • Co-op: each seat has its own odds sets; only single-player is supported.
  • A profile's very first run has scripted early packs; leave 'first run' unknown unless you are certain.

Position in the pack

Slot by slot

Rarity of each card slot
CardRareUncommonCommon
#10%35%65%
#20%36%64%
#30%37%63%

Slots are not independent: a non-rare card raises the next slot’s rare chance by one point, and a rare drops it back to −5. Each row is that slot’s exact marginal chance.

Pity counter

Where you are on the curve

Chance of at least one rare in a 3-card normal fight pack, by counterThe chance climbs from the starting offset to its cap; a rare resets it to the left edge.0%25%50%75%100%081523303845you · 0%Non-rare cards since last rareP(≥1 rare in pack)

Card appearance

Will this specific card show up?

Exact
Cards your profile has unlocked

Only cards that can appear in a normal reward are listed.

Pick a card to see the exact chance it appears in this pack.