Spells in Noita are organised into tiers which dictate which spells can spawn; each biome selects one or more tiers of spells and wands to spawn when generating spell shops and wands. Most spells belong to more than one tier, though it may define a different rarity value for each tier (for example, a spell may be very common for Tier 1, but exceedingly rare in Tier 3).
Wand generators pull spells from one tier lower, so a tier 3 wand will have tier 2 spells in it for example. There is also a 10% chance that a wand will take a projectile from a higher tier. This check is done multiple times until the 10% roll fails, meaning the chosen projectile can be from many tiers higher. The projectile fills the rest of the available slots after modifiers and multicasts have been put in.
Spellshop tiers are set by the depth they appear in, unless they are forced to spawn spells from a specific tier. Most early biomes force a specific tier. Vault and Temple spellshops are set by the depth. Any spellshop deeper than Temple will be tier 6. Hell and Sky force spells to spawn from tier 10.
Spellshops can spawn any type of spell, but wands can only spawn with multicasts, projectiles, or modifiers. This means that material, utility, static projectile and other type spells can only be found from spellshops, secret rooms or chests.
