A seed fixes every random result of a run. Two players on the same seed start from the same results, but each choice they make can change what they see next.
StS1 seed codes
A StS1 seed uses the digits 0 to 9 and the letters A to Z without O. Typing O enters 0. The game never generates a random seed that contains an offensive word.
What an StS1 seed decides
StS1 splits the seed into separate random streams, so one kind of roll does not shift another:
| Stream | Decides |
|---|---|
| Map | Each act's map layout and rooms |
| Monsters | Which fights you meet, and the boss order |
| Events | What each ? room becomes, which event appears, event outcomes |
| Merchant | Merchant stock, prices and the sale card |
| Cards | Card reward rarity, colorless card rarity, curses |
| Treasure | Chest size and contents, fight gold, elite relic rarity |
| Relics | Relic rarity rolls and the order of each relic list |
| Potions | Potion drop chance, potion rarity and which potion |
| Monster HP | Enemy HP within its range |
| Monster AI | Enemy move choices |
| Shuffle | Draw pile shuffles |
| Card generation | Random cards created during combat |
| Misc | Boss gold and other small rolls |
The map is the same for everyone on a seed, since each act's map comes from the seed alone.
The last five streams (monster HP, monster AI, shuffle, card generation and misc) restart on every floor from the seed and the floor number. Your shuffles and enemy moves on a floor do not depend on how many shuffles or turns you had before it.
At the start of acts 2, 3 and 4 the card stream jumps ahead to a fixed point (the 250th, 500th or 750th roll). Card rewards in the new act start from the same point on that seed no matter how many card rewards you saw before, as long as you stayed below that point.
StS1's Neow uses its own stream built from the seed, so Neow's four offers depend only on the seed. See Neow blessings.
What an StS2 seed decides
A StS2 seed is 12 letters and numbers. At the start of the run the game generates, from the seed alone:
- which act 1 you get (Overgrowth or Underdocks),
- each act's fights, events and boss, in order,
- each act's map,
- which Ancients appear in acts 2 and 3.
Other streams cover draw pile shuffles, what ? rooms become, monster moves, random cards, potions, targets and orbs during combat, and which player gets a relic when several pick the same one.
Each player has their own streams for card, potion and relic rewards, Merchant stock and prices, and card transformations. In co-op one player's rewards never change another's.
Since version v0.107.1 the streams use a new random generator. Before it, some streams were correlated, so one result (such as act 1) hinted at another (such as the curse from Neow's Bones).
What the seed does not fix
In both games, anything that depends on a choice can change: which rooms you enter, which rewards you take and which cards you play decide how far each stream has moved. The StS1 Daily Climb gives everyone the same seed, character and modifiers each day; see the Daily Climb tool.