Every organ seals one door with living tissue. The gene that opens it waits in a gene chamber guarded by a key guardian mini-boss, and every organ has a different guardian. Beat it, splice the gene into yourself, and the gene's bonus stays with you for the rest of the run.
Each organ seals one doorway with a mucus plug, a tight junction or a fibrin clot. It won't open until you carry that organ's gene.
About two times in three the sealed door is on the way to the boss. Otherwise it locks the organ's Upgrade Chamber
Walk into it without the gene and you're turned back: "SEALED BY A MUCUS PLUG / TIGHT JUNCTION / FIBRIN CLOT: find the Mucolytic Enzyme / Fusion Peptide / Plasminogen Activator somewhere on this organ"
Carry the right gene and the door dissolves for good: "DISSOLVED", "FUSED THROUGH" or "CLOT LYSED"
A fight room holding a strand of foreign DNA you can splice into yourself, guarded by the organ's key guardian.
Always placed so you can reach it without passing the sealed door, often in a dead end
Entering it announces its KEY GUARDIAN. When the gene appears: "GENE CHAMBER: a strand of foreign DNA you can splice into yourself"
When the guardian falls, the gene appears in the middle of the room as a glowing helix. Walk into it to take it
Each gene opens its door type and gives a passive bonus for the rest of the run
From the Codex
Viruses carry genes for tools that break host barriers, like neuraminidase that cuts through mucus, or fusion peptides that merge viral and cell membranes.
Fun fact: Neuraminidase is the target of Tamiflu: block it, and new flu virions get stuck to the cell they came from.
Guardians are mini-bosses labelled KEY GUARDIAN. Each gene's guardian gets meaner every time you meet it deeper in the body.
Stages: the second organ with the same gene meets an AWAKENED guardian and the third meets an ANCIENT one. Each stage adds +25% health, +15% damage, 15% faster attacks and more projectiles or adds
The first guardian (Nasal Passage) is a lighter test: 40% health and 55% damage
Every guardian throws a hook every 2.25–3.25 s after a 0.45 s warning line. 95% of throws are aimed where you're going. If it catches you, you take 8 damage and get reeled in for up to 2.5 s with no dashing out ("HOOKED!")
Each one also fires its own aimed shot every 0.9–1.8 s
Below half health its attacks come 25% faster
Too big to be flung into pits or shoved by hazards
Defeat drops nucleotides, Polymerase Shards (6, +3 per stage), Chaperone Proteins (half of 1, +1 per stage), a 35% chance of gear and about a 9% chance of RNA, then the gene
From the Codex
Each organ seals one door until you carry the right gene.
Fun fact: Genes also give a passive bonus, like mucus or clots no longer slowing you.
A giant cell with many nuclei, formed when neighbouring cells fuse their membranes into one. Viruses like RSV and measles cause them with their fusion proteins.
Fun fact: Your muscle fibres and part of the placenta are natural syncytia; the placenta's fusion gene came from an ancient retrovirus.
A star-shaped scaffold cell (Awakened) guarding the Plasminogen Activator. It strings a cage of conduit threads around you that closes to nothing.
Darts in quick hops to a new spot around you, then rests a moment
Conduit Web: 6 anchors land in a ring around you, the threads flicker for 0.7 s, then go live and pull the ring shut over 1.1 s. One side is always left open, or dash across a thread
Sweep: it anchors itself and swings a long thread through a wide arc around itself after its reach flashes
Conduit Volley: two waves of 6 shots down its arms
Fibroblastic reticular cells: star-shaped cells that weave a lymph node's scaffolding, wrapping collagen fibres into conduits that carry small molecules from the lymph straight to waiting immune cells.
Fun fact: Immune cells crawl along this network like roads, and the same cells release the chemokines that guide T cells to their zone.
The gut's electrical pacemaker (Awakened), guarding the Mucolytic Enzyme. It sets the whole room contracting.
Peristalsis: 2 bands of contraction roll from wall to wall across the whole room, each with a gap to slip through. The gap glows green at the wall first, and getting caught hurts and shoves you
Segmentation: the floor splits into 6 strips and alternate strips flash and clench in turn, so you hop from strip to strip
Mucin Spray: a fan of 7 slowing globs
Aimed shot: one big slowing glob
Keeps a middle distance, circling, and pulses with a steady electrical beat
Hepatocytes are the liver's main cells and do most of its metabolism and detox. Many carry extra chromosome sets or two nuclei (polyploidy), and each works differently depending on its zone between the portal and central veins.
Fun fact: The liver can grow back from as little as a third of its mass, mostly by its hepatocytes dividing again.
A huge bone-dissolving cell (Ancient) guarding the Mucolytic Enzyme. It burrows after you and erupts where it surfaces.
Burrowing: it sinks out of reach for 2.2 s while a crack tracks you, then erupts after a 0.7 s warning circle in a ring of 14 bone shards, leaving a resorption pit that hurts to stand in for 5 s. As an Ancient guardian it burrows and erupts twice in a row
Acid Etch: 5 lobs that dissolve damaging pits into the floor
Trabecular Collapse: bone gives way in a rolling line of 9 marked circles toward you and past
A huge cell with many nuclei that dissolves bone: it seals onto the surface and pumps out acid and enzymes under its ruffled border. With bone-building osteoblasts it constantly remodels the skeleton.
Fun fact: Thanks to osteoclasts and osteoblasts, about a tenth of your skeleton is replaced every year.
Giant pyramidal neurons of the motor cortex, the biggest nerve cells in the brain. Their axons run all the way down the spinal cord to drive your muscles.
Fun fact: Signals jump between the gaps in an axon's myelin sheath (saltatory conduction) at over 100 metres per second.
