Use difficulty-gated rooms to find extra cells and useful route rewards.
PC / Global, base game and installed DLC routes labeled
WHERE & HOW TO FARM
Where to farm
BSC-marked doors in biomes and passages, when the required Boss Stem Cells are active in the current run.
Boss Stem Cell doors are optional route gates. Their displayed requirement tells you how many cells must be active for the current run. Eligible doors may lead to cell vats, shops, treasure rooms, or shortcuts, so read the sign and decide whether the detour suits your build and health. The contents are not guaranteed to be a vat every time.
Activate enough BSCs in the starting tube before beginning the route.
Reach a marked door and have enough health to continue through the biome.
At the start, set the BSC level you intend to play; the unlock existing in your save is not enough by itself.
As you traverse a biome, inspect the number on each BSC door.
Compare its requirement with the BSC count active for this run.
Open the door only when it is available and the reward or branch is worth the detour.
Explore the room or passage behind it and collect its visible rewards, including any cell vat present.
Return to the main route and preserve enough health for the added difficulty.
At the next Collector passage, spend collected cells on a desired blueprint.
Farming tips
An eligible door lights blue; check each sign because requirements vary by door.
Higher BSC difficulty raises cell drops, but also makes the route more demanding; choose a level you can clear consistently.
Repeat, collect and use
Repeatable on runs where your active BSC count meets a door’s requirement. Specific rooms are route-dependent, and a door is unavailable below its threshold.
Common mistakes
Expecting every BSC door to contain a cell vat; doors can reveal other rewards or a shortcut, so inspect what is actually there.
Looking for the door with too few active cells; activate the requirement before leaving the starting tube.
Taking every detour automatically; account for the harder biome and your current health before entering.
When to stop or switch
Leave the BSC branch once you have collected its available reward or the extra route threatens your run; spend the cells at the next Collector.
