Boss Stem Cell

**Boss Stem Cells** (or simply **Boss Cells**) are permanent items that increase the difficulty of the game when active. The first one is acquired by beating the Hand of the King or the Queen with no Boss Stem Cells active, the second by beating either with one active, and so on. However, the fifth Boss Stem Cell is obtained by beating the Giant with four active. The use of Aspects prevents the acquirement of the next Boss Stem Cell.

Boss Stem Cells can be injected and removed at the start of the game in the Tube, as long as one hasn't left the starting area. Each one makes the game significantly harder by increasing enemy tier, density, variety, and limiting healing options. On the other hand, higher difficulty levels also increase cells dropped from enemies and the level of the Legendary Forge, and allow access to new blueprints and bonus doors scattered through the levels, as well as some that are dropped by enemies exclusive to high BSCs. The bonus doors show the number of Boss Stem Cells required to enter and will shine blue if enough are currently active.

## Modifiers

* The early phases of bosses change.
* Health Fountains are only available at every other Passage, those without them will instead contain a Flask recharge.
* Improves the cap of the Legendary Forge, allowing you to upgrade the frequency of ++ items to 100%.
* Unlocks a door in Prison Depths that leads to the Ancient Sewers.
* Unlocks a door in Corrupted Prison that leads to the Ramparts.
* The early phases of bosses change.
* Removes all Health Fountains from Passages, but they will still contain one Flask charge each.
* Improves the cap of the Legendary Forge, allowing you to upgrade the frequency of S items to 25%.
* Multiplies the amount of cells dropped by enemies by 2.
* Unlocks a door in Slumbering Sanctuary that leads to the Cavern.
* Unlocks a door in Forgotten Sepulcher that leads to Guardian's Haven.
* The early phases of bosses change.
* Passages now only contain 2 Flask charges in total, one after the first boss and the other before the second boss.
* Improves the cap of the Legendary Forge, allowing you to upgrade the frequency of S items to 50%.
* Multiplies the amount of cells dropped by enemies by 2.
* Allows you to collect Scroll Fragments.
* Increases item levels by +1.
* Colorless items from Cursed Chests are improved from ++ to S-quality.
* Unlocks a door in Ramparts that leads to the Insufferable Crypt.
* The early phases of bosses change.
* Increases the detection range of mobs and gives most of them the ability to teleport to you.
* Passages don't contain any Flask charges.
* Improves the cap of the Legendary Forge, allowing you to upgrade the frequency of S items to 100%.
* Multiplies the amount of cells by enemies by 3.
* Allows you to collect more Scroll Fragments than on the Expert Difficulty.
* Increases item levels by +3.
* Colorless items from Cursed Chests are improved from ++ to S-quality.
* The early phases of bosses change.
* Increases the detection range of mobs and gives most of them the ability to teleport to you.
* The Malaise is activated.
* Passages don't contain any Flask charges.
* Improves the cap of the Legendary Forge, allowing you to upgrade the frequency of S items to 100%.
* Multiplies the amount of cells dropped by enemies by 3.
* Allows you to collect more Scroll Fragments than on the Expert Difficulty.
* Increases item levels by +3.
* Colorless items from Cursed Chests are improved from ++ to S-quality.
* Gives access to the Astrolab and the Observatory, which are located at the end of Throne Room.
* The Collector's Intern replaces the Collector in Passages.

## Trivia

* When Boss Stem Cells, then named *Boss Runes*, were added in the *v0.5.3* patch of the Foundry Update, they could all be obtained on 0 BSC difficulty and each was dropped by a different boss.

## History

* 1.2: Introduced 5 BSC difficulty.
* 1.9: Removed Legendary item improvements from 3+ BSC that added one stat of each color.
	+ Does not apply to the Hunter's Grenade.
* 2.3: Adjusted BSC difficulty curve:
	+ 2 BSC now grants a flask recharge in every Passage.
	+ 3 BSC now grants a flask recharge before the first boss and after the second boss.
	+ 4 BSC no longer has the Malaise mechanic.
* 3.0: The Hunter's Grenade no longer provides stats.

## Gallery

* Closed Door
1 Boss Cell
* Opened Door
* Locked Door
2 Boss Cells
* Locked Door
3 Boss Cells
* Locked Door
4 Boss Cells
* Locked Door
5 Boss Cells