Boss Stem Cells

Boss Stem Cell
Location(s)	The Hand of the King, The Giant (only for the fifth 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 with no Boss Stem Cells active, the second by beating him with one active, and so on. However, the fifth Boss Stem Cell is obtained by beating the Giant with four active.

Boss Stem Cells can be injected and removed at the start of the game in the Tube. 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 ones dropped by enemies exclusive to high BSCs. The doors show the number of Boss Stem Cells required to enter and shine blue if enough are currently active. The fifth Boss Cell is special in that it doesn't modify anything compared to the fourth until the Throne Room, where it grants access to a secret biome, the Astrolab, and the hidden final boss of the game in the Observatory.

Modifiers

# of Boss Stem Cells	Modifiers
	- Hard difficulty - Reduce number of health fountains (only available every other level); transition areas without health fountains will instead give a mini recharge that will refill one use of health flask + Improves the level of the Legendary Forge by allowing you to increase the frequency of + and ++ items up to 100% + Unlocks a door in Prison Depths that goes to the Ancient Sewers + Unlocks a door in Corrupted Prison that goes to the Ramparts + Allows you to collect the next Boss Stem Cell + Bosses skip their first phase
	- Very Hard difficulty - Removes all health fountains and flask recharges within transition areas. A single flask recharge is dropped after the first boss and before the second. They can still be purchased from food shops. + Improves the level of the Legendary Forge by allowing you to increase the frequency of S items up to 25% + Multiplies the amount of dropped cells by 2 (effect also applies to cells found in containers) + Unlocks a door in Slumbering Sanctuary that goes to the Cavern + Unlocks a door in Forgotten Sepulcher that goes to Guardian's Haven + Allows you to collect the next Boss Stem Cell + Bosses skip their first phase
	- Expert difficulty - Flask recharges are only obtained from food shops. + Improves the level of the Legendary Forge by allowing you to increase the frequency of S items up to 50% + Multiplies the amount of dropped cells by 2 (effect also applies to cells found in containers) + Allows you to collect Scroll Fragments + Legendary items and colorless items are improved. + Unlocks a door in Ramparts that goes to the Insufferable Crypt + Allows you to collect the next Boss Stem Cell + Bosses skip their first phase
	- Nightmare difficulty - Increases detection range of mobs and gives most of them the ability to teleport next to your position. - Flask recharges are only obtained from food shops. + Malaise is activated. See the main article for information about malaise. + Improves the level of the Legendary Forge by allowing you to increase the frequency of S items up to 100% + Multiplies the amount of dropped cells by 3 (effect also applies to cells found in containers) + Allows you to collect more Scroll Fragments + Legendary items and colorless items are improved. + Allows you to collect the next Boss Stem Cell from The Giant + Bosses skip their first phase
	- Hell difficulty - Increases detection range of mobs and gives most of them the ability to teleport next to your position. - Flask recharges are only obtained from food shops. + Malaise is activated. See the main article for information about malaise. + Improves the level of the Legendary Forge by allowing you to increase the frequency of S items up to 100% + Multiplies the amount of dropped cells by 3 (effect also applies to cells found in containers) + Allows you to collect more Scroll Fragments + Legendary items and colorless items are improved. + Gives access to the Astrolab and the Observatory (Rise of the Giant DLC content). Entrance to The Astrolab is located at the end of Throne Room. + Bosses skip their first phase

Doors

• 

  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

Notes

• Until v1.9, at 3+ BSC, Legendary items gave +1 to all Stats. This now only applies to the Hunter's Grenade.
• Until v1.2, the fifth boss cell was unobtainable (unless with third party tools), and a 5 BSC door in the Graveyard would grant access to the unfinished level Repository of the Architects.
• When boss cells, or then named boss runes, were added In the v0.5.3 patch of the foundry update they could all be obtained on the 0 BSC difficulty and each was dropped by a different boss.