Blueprints

Blueprints are items that are used to unlock new Gear, Mutations, Upgrades and Outfits. They can be found by killing enemies or in secret areas blocked by keys, rune requirements, puzzles, timed doors or are just hidden. Some are limited by Boss Stem Cells, either they do not drop on lower difficulty levels, or the items or pathways required to get them are limited by Boss Stem Cells.

When a blueprint is found, the player has to talk to the Collector in any biome transition to deliver it and be able to unlock it. They can be unlocked by paying cells for them at the Collector. Once the total cell cost has been payed, the item can be found in throughout game, selected from the Tailor or bought from Guillain.

A blueprint is lost for the run when the player dies before delivering it to the Collector.

Rarity
Blueprints have 5 rarity levels, each with a precise drop chance.
 * Always: 100% (68 blueprints)
 * Common: 10% (20 blueprints)
 * Uncommon: 1.7% (31 blueprints)
 * Rare: 0.4% (62 blueprints)
 * Legendary: 0.03% (2 blueprints)

Note that for the always rarity, the majority of drops from bosses are on a specific BSC difficulty as seen in the table below. Killing a boss on a higher difficulty will also drop the blueprint that is next in sequence to drop from the boss, so if a blueprint from a lower difficulty remains, that will drop before the blueprint that corresponds to the current difficulty.

Secret blueprints
There are 42 blueprints which do not drop from enemies or bosses, but are found in secret areas, at the end of a puzzle, inside a timed door, in rune exclusive areas, locked doors or are rewarded after completing a certain number of Daily Runs.

Although most of these are generated on all difficulties, some require items or routes that are only accessible on higher difficulty levels. A few are only available after a certain amount of runs have been attempted.

There are also 2 blueprints that drop from the 5 BSC exclusive boss but have a secret requirement. Information on how to find these can be found on the Gear, Mutations, Outfits and The Collector pages.

Drop rates
During level generation a there is a chance based on rarity that a blueprint gets assigned to a viable enemy for it to drop from. So if level generation assigns a blueprint to an enemy, the player will need to kill that specific enemy to get the blueprint.

Drop limit
The dropping of blueprints from enemies is limited to 1 blueprint per biome in total. Even if there are multiple blueprints with 100% drop rate.
 * This limit can only be exceeded with the Hunter's Grenade.
 * This limit does not apply or is not influenced by blueprints found in secret areas.

Hunter's Mirror
The Hunter's Mirror is an upgrade offered by the Collector. When unlocked, a mirror appears at the start of the Prisoners' Quarters, next to the Scribe. When interacted with, it shows a random enemy or boss that carries a blueprint not currently acquired. It does not show any items that cannot be unlocked at the current set difficulty level, but it can show enemies found in inaccessible biomes.

Hunter's Grenade
See the main article for information about the hunter's grenade.

A blueprint drop can be forced by using the. When used on an enemy, it will transform into an elite version of itself, or if that is not possible, an elite Zombie and drop the. Damage the elite until a message pop-ups informing the player to use the extractor. Use it and the elite enemy dies and drops a random blueprint from its remaining blueprint pool.