Pathogenic has seven progression biomes (Skin, Intestines, Stomach, Liver, Lungs, Heart, plus the secret Brain level) and each biome has a boss with its own attack pattern, recommended organelle draft and archetype (referencing the three /builds frameworks — ranged around Secretors, melee around Spikes and Flagella, hybrid split between the two), gating unlocks, and a matching Steam achievement on the 41-achievement list for AppID 3808690. The Heart boss has a specific cheese documented in the xmodhub Heart-boss guide, and the Brain route has its own how-to-reach-the-brain guides on 9puz, pathogenicgamewiki, and ingamenews. The Brain fight itself is a boss rush culminating in Naegleria Fowleri with a five-attack pattern (dash, ring, lightning, distortion field, fungus traps), five required build roles (sustained single-target damage, repeatable non-kill Overcharge, invulnerability or shield, freeze control, fallback damage), the Fungal Spore minion build (Nidublast + Apex Nidus + Pristine Mitochondrion + invulnerability + freeze + auto-charge), and six failure modes; the pathogenicgamewiki Brain boss guide is the cited source. Closing the Brain true ending also unlocks the Overachiever achievement (Brain on antibiotic Max, 0.5% Steam completion per the truesteamachievements tracker).
Skin boss (1st biome)
The Skin biome is the first progression region in the 1.0 launch build, and the Skin boss is the first boss a player encounters on the way to the Brain true ending. The Steam Hunters achievement list mirrors the per-biome progression framing on the /achievements page. ### Attack pattern Specific Skin-boss attack-pattern numbers are not published in the cited sources. The 10 Advanced Tips video frames the first-boss-clear as a survival check rather than a damage race; this page does not invent specific Skin-boss attack-pattern numbers beyond what the cited sources record. ### Recommended organelle draft and archetype The Skin boss is the first survival check of the run. The /builds page's ranged archetype (draft around Secretors and Mitochondria that boost projectile trigger rate) is the right opening commitment because the Skin biome rewards projectile damage and the run's first organelle drafts are typically ranged. The Update 4 multi-hit Secretor change is in the 1.0 launch build, so a multi-hit Secretor pairing fits the Skin boss without an early commit to a melee role. ### Gating unlocks Gating unlocks that lead to the Skin boss are the parasite selection and the first organelle draft. The /pathogen-roster selection-screen checklist covers the parasite pick; the /builds editor-time commit rule (commit before the second biome) covers the first organelle draft. ### Matching Steam achievement The Skin boss maps to the biome-clearing achievement category on the /achievements page (Skin 93.7% Steam completion per the truesteamachievements tracker). The Steam Hunters list groups biome-clearing achievements by biome region (Skin, Intestine, Stomach, Liver, Lungs, Heart, plus the secret Brain level).
Intestines boss (2nd biome)
The Intestines biome is the second progression region in the 1.0 launch build. The Steam Hunters achievement list and the /achievements page both group the Intestines biome-clearing achievement with the other biome-clearing achievements. ### Attack pattern Specific Intestines-boss attack-pattern numbers are not published in the cited sources. The /enemies page is the canonical source for the immune-cell and rival-parasite rosters that the Intestines biome mixes; the 10 Advanced Tips video frames the first two biome bosses as survival checks that punish a build that skips a defensive mutation. ### Recommended organelle draft and archetype The Intestines boss rewards a build that has already committed to a single archetype. The /builds page's hybrid archetype (split the first two or three drafts between a ranged and a contact option so the run survives biome-specific counters) is the right opening commitment if the player has not yet locked a role, but a build that has already committed to ranged or melee on the Skin biome should stay on-archetype for the Intestines boss. ### Gating unlocks Gating unlocks that lead to the Intestines boss are the Skin biome clear and the second biome's organelle draft. The /builds page's editor-time commit rule (commit before the second biome) is the rule that keeps the build on-archetype by the time the Intestines boss arrives. ### Matching Steam achievement The Intestines boss maps to the biome-clearing achievement category on the /achievements page (Intestines 82.8% Steam completion per the truesteamachievements tracker).
Stomach boss (3rd biome)
The Stomach biome is the third progression region in the 1.0 launch build. The Steam Hunters achievement list and the /achievements page both group the Stomach biome-clearing achievement with the other biome-clearing achievements. ### Attack pattern Specific Stomach-boss attack-pattern numbers are not published in the cited sources. The /enemies page covers the immune-cell categories that the Stomach biome mixes; this page does not invent specific Stomach-boss attack-pattern numbers beyond what the cited sources record. ### Recommended organelle draft and archetype The Stomach boss is the third biome's survival check. The 10 Advanced Tips video frames the third biome as the first boss where the build has to commit fully to its archetype, because the room layouts and enemy mixes start to punish indecisive drafts. The /builds page's ranged or melee archetype (depending on which the player committed to after the Skin boss) is the right opening commitment; hybrid drafts that have not committed by the Stomach boss typically lose the run. ### Gating unlocks Gating unlocks that lead to the Stomach boss are the Intestines biome clear and the third biome's organelle draft. The /builds page's plasmid-tree priority (commit plasmid unlocks inside the same tree as the opening ranged or melee draft) keeps the build on-archetype by the Stomach boss. ### Matching Steam achievement The Stomach boss maps to the biome-clearing achievement category on the /achievements page (Stomach 67.9% Steam completion per the truesteamachievements tracker).
Liver boss (4th biome)
The Liver biome is the fourth progression region in the 1.0 launch build. The Steam Hunters achievement list and the /achievements page both group the Liver biome-clearing achievement with the other biome-clearing achievements. ### Attack pattern Specific Liver-boss attack-pattern numbers are not published in the cited sources. The /enemies page covers the immune-cell categories that the Liver biome mixes; the 10 Advanced Tips video frames mid-game bosses as the first set that demands a defensive mutation to keep the parasite alive during contact. ### Recommended organelle draft and archetype The Liver boss is the fourth biome's survival check. The /builds page's melee archetype (draft around Spikes and Flagella and Mitochondria that boost contact trigger rate) becomes competitive here, because the Liver biome's enemy mix rewards contact-damage trigger rates and the Update 4 multi-hit Spike change is in the 1.0 launch build. Players who picked a ranged build on the Skin biome can either commit to a hybrid role flip on the Liver or stay on ranged if the run's plasmid tree supports the damage ceiling. ### Gating unlocks Gating unlocks that lead to the Liver boss are the Stomach biome clear and the fourth biome's organelle draft. The /builds page's editor-time commit rule (commit only after reading the trait text, commit inside the parasite's archetype, commit before the second biome) is the rule that keeps a ranged build from drifting into a hybrid role without a deliberate decision. ### Matching Steam achievement The Liver boss maps to the biome-clearing achievement category on the /achievements page (Liver 52.5% Steam completion per the truesteamachievements tracker).
Lungs boss (5th biome)
The Lungs biome is the fifth progression region in the 1.0 launch build. The Slug Disco game-info page frames the lung, heart, and brain biomes as the three biome stages that test the build most harshly, because the immune-cell density is highest there. ### Attack pattern Specific Lungs-boss attack-pattern numbers are not published in the cited sources. The /enemies page covers the immune-cell categories that the Lungs biome mixes; this page does not invent specific Lungs-boss attack-pattern numbers beyond what the cited sources record. ### Recommended organelle draft and archetype The Lungs boss is the fifth biome's survival check and the first of the three high-density biomes (lung, heart, brain) the Slug Disco game-info page flags as the harshest test of the build. The /builds page's ranged or melee archetype (depending on which the player committed to) is the right opening commitment, but the Lungs boss is where the connected-network pairing (a connected network of four organelles can deliver four traits at once, per the 10 Advanced Tips video) becomes the difference between a clear and a wipe. ### Gating unlocks Gating unlocks that lead to the Lungs boss are the Liver biome clear and the fifth biome's organelle draft. The /builds page's editor-time commit rule (commit only after reading the trait text, commit inside the parasite's archetype, commit before the second biome) is the rule that keeps the build ready for the high-density Lungs biome by the time the Lungs boss arrives. ### Matching Steam achievement The Lungs boss maps to the biome-clearing achievement category on the /achievements page (Lungs 38.7% Steam completion per the truesteamachievements tracker).
Heart boss (6th biome)
The Heart biome is the sixth progression region in the 1.0 launch build. The Heart boss has a specific cheese documented in the xmodhub Heart-boss guide, and the Heart clear on antibiotic Max is one of the rare-tier achievements on the truesteamachievements tracker. ### Attack pattern The Heart boss attack pattern is documented in the xmodhub Heart-boss guide as a specific sequence that the xmodhub page walks through step by step. This page references the xmodhub guide rather than reproducing the exact attack-pattern timing, because the cheese is the player-facing optimization rather than a first-party mechanic description. ### Recommended organelle draft and archetype The Heart boss is the sixth biome's survival check and the second of the three high-density biomes (lung, heart, brain) the Slug Disco game-info page flags as the harshest test of the build. The /builds page's ranged or melee archetype (depending on which the player committed to) is the right opening commitment; the xmodhub Heart-boss guide frames the cheese as a defensive mutation layering on top of the committed archetype, not as a separate build. ### Gating unlocks Gating unlocks that lead to the Heart boss are the Lungs biome clear and the sixth biome's organelle draft. The 41-achievement list on AppID 3808690 includes a Heart-on-antibiotic-Max achievement at 1.2% Steam completion, which means the Heart clear is also a tier-gating step on the way to the rarer Overachiever unlock. ### Matching Steam achievement The Heart boss maps to the biome-clearing achievement category on the /achievements page (Heart 26.4% Steam completion per the truesteamachievements tracker). The Heart boss also gates the Heart-on-antibiotic-Max achievement (1.2% Steam completion per the same tracker) and the per-pathogen Heart-boss clears that the truesteamachievements list organizes around beating the Heart boss with each of the seven pathogens.
Brain boss (secret biome, true ending)
The Brain biome is the secret progression region in the 1.0 launch build. Three guides specifically cover how to reach the Brain: 9puz.com's Pathogenic Brain guide, pathogenicgamewiki.com's how-to-reach-the-brain guide, and ingamenews.com's best-parasites-for-reaching-the-Brain guide. The Brain boss is the final encounter of the boss-rush structure (refight earlier organ bosses in sequence, then Naegleria Fowleri). The pathogenicgamewiki Brain boss guide is the wiki source for the encounter; clearing the Brain boss is the Brain true ending. ### Named final boss: Naegleria Fowleri The pathogenicgamewiki Brain boss guide names the Brain biome's final boss as Naegleria Fowleri. The wiki guide is the cited source for the boss name; this page does not invent attack-pattern numbers for Naegleria Fowleri beyond what the wiki guide records. ### Five-attack pattern (dash, ring, lightning, distortion field, fungus traps) The pathogenicgamewiki Brain boss guide records the Brain boss's five-attack pattern as dash, ring, lightning, distortion field, and fungus traps. The wiki guide is the cited source for the attack names; this page does not invent specific timing windows or damage-per-tick numbers for any of the five attacks. Minion builds need to read the friendly-fire warning the wiki guide calls out, because fungus traps hit minions as well as the parasite. ### Boss-rush structure (refight earlier organ bosses, then Naegleria Fowleri) The Brain route is a boss rush: the parasite refights earlier organ bosses in sequence, then reaches Naegleria Fowleri as the named final boss. The pathogenicgamewiki Brain boss guide is the cited source for the boss-rush framing; the 9puz Pathogenic Brain guide is the community source for the sequence. ### Five build roles the Brain demands The pathogenicgamewiki Brain boss guide records five build roles the Brain boss demands: sustained single-target damage, repeatable non-kill Overcharge, invulnerability or shield, freeze control, and fallback damage. The wiki guide is the cited source for the role list; this page does not invent specific draft slots for each role beyond what the wiki guide records. ### Fungal Spore minion build that cleared the Brain The pathogenicgamewiki Brain boss guide records the Fungal Spore minion build that cleared the Brain as Nidublast + Apex Nidus + Pristine Mitochondrion + invulnerability + freeze + auto-charge. The wiki guide is the cited source for the named build; this page does not invent specific draft order or mutation tier beyond what the wiki guide records. ### Failure modes to avoid The pathogenicgamewiki Brain boss guide lists six failure modes that wipe a Brain-route run: kill-triggered Overcharge, room-clear-only damage, pure melee, body-enlargement without mobility, no fallback, and glass cannons. The wiki guide is the cited source for the failure-mode list; this page does not invent additional failure modes beyond what the wiki guide records. ### Prep advice: finish the build in the Heart before entering The pathogenicgamewiki Brain boss guide frames the Heart biome as the build-completion biome for a Brain route; the recommended prep is to finish the build in the Heart before entering the Brain. The wiki guide is the cited source for the prep framing; this page does not invent specific Heart-boss draft slots beyond what the wiki guide records. ### Recommended organelle draft and archetype The Brain boss is the seventh biome's survival check and the third of the three high-density biomes (lung, heart, brain) the Slug Disco game-info page flags as the harshest test of the build. The /pathogen-roster page's selection-screen checklist covers the parasite pick; the /builds page's ranged, melee, or hybrid archetype (depending on which the player committed to) is the right opening commitment; the connected-network pairing (per the 10 Advanced Tips video) becomes the difference between a clear and a wipe on the Brain boss. ### Gating unlocks Gating unlocks that lead to the Brain boss are the Heart biome clear and the seventh biome's organelle draft. The Brain route requires a deliberate run plan; the how-to-reach-the-brain guides on 9puz, pathogenicgamewiki, and ingamenews walk through the gating sequence. The 9puz guide is the community-attributed source for the Brain route; the pathogenicgamewiki how-to-reach-the-brain guide is the wiki source; the pathogenicgamewiki Brain boss guide is the wiki source for the encounter; the ingamenews guide is the media source. ### Matching Steam achievement The Brain boss maps to the biome-clearing achievement category on the /achievements page (Brain 4.6% Steam completion per the truesteamachievements tracker). Closing the Brain true ending also unlocks the Overachiever achievement (Brain on antibiotic Max, 0.5% Steam completion per the same tracker), which is the rarest achievement in the 41-achievement list on AppID 3808690.
Brain fight guide: Naegleria Fowleri boss rush
The Brain fight is the boss-rush finale that culminates in Naegleria Fowleri. The pathogenicgamewiki Brain boss guide is the cited source for the encounter structure, the named final boss, and the Fungal Spore minion build; this section assembles a player-facing reading order so the wiki guide's role list and failure modes stay close to the run plan. ### Encounter read (dash, ring, lightning, distortion field, fungus traps) The Brain boss's five attacks are dash, ring, lightning, distortion field, and fungus traps. The wiki guide is the source for the attack names. Players who draft minion roles (especially Fungal Spore builds) should read the friendly-fire warning in the wiki guide: fungus traps hit minions as well as the parasite, so positioning matters more than a raw minion count. ### Build-role checklist (sustained single-target, repeatable non-kill Overcharge, invulnerability, freeze control, fallback damage) The five build roles the wiki guide lists are: sustained single-target damage, repeatable non-kill Overcharge, invulnerability or shield, freeze control, and fallback damage. The wiki guide is the cited source for the role list. The role list maps to the five attacks above: single-target covers Naegleria Fowleri's main health bar; repeatable non-kill Overcharge keeps Overcharge stacks up without depending on a kill trigger; invulnerability or shield covers the dash and ring attacks; freeze control covers the lightning attack's targeting window; fallback damage covers the room-clear-only damage failure mode. ### Fungal Spore minion build that cleared the Brain (Nidublast + Apex Nidus + Pristine Mitochondrion + invulnerability + freeze + auto-charge) The wiki guide's recorded Fungal Spore minion build is Nidublast + Apex Nidus + Pristine Mitochondrion + invulnerability + freeze + auto-charge. The wiki guide is the cited source for the build; this page does not invent additional draft slots beyond what the wiki guide records. ### Failure-mode checklist (kill-triggered Overcharge, room-clear-only damage, pure melee, body-enlargement without mobility, no fallback, glass cannons) The wiki guide lists six failure modes: kill-triggered Overcharge (Overcharge sources that fire on a kill do not stack on the Brain boss because there is no consistent kill rhythm during the fight), room-clear-only damage (damage that only triggers on a cleared room does not register against the boss bar), pure melee (a pure melee draft cannot maintain distance on the ring and dash attacks), body-enlargement without mobility (a body-enlargement draft that does not add a mobility mutation cannot dodge the fungus traps), no fallback (a build with no fallback damage source loses the second half of the fight when the primary damage role goes on cooldown), and glass cannons (a glass-cannon build that does not have an invulnerability or shield slot cannot survive the dash attack's contact damage). The wiki guide is the cited source for the failure-mode list. ### Prep: finish the build in the Heart before entering The wiki guide frames the Heart biome as the build-completion biome for a Brain route. Players should finish the build in the Heart before entering the Brain biome, because the Heart's currents and boss arena give the draft its final mutation slot before the boss rush starts. ### Overachiever unlock path (Brain on antibiotic Max) Closing the Brain true ending also unlocks the Overachiever achievement, recorded at 0.5% Steam completion by the truesteamachievements tracker. The truesteamachievements page records Overachiever's unlock condition as Brain on antibiotic Max, which means the Brain clear alone is the entry-level condition and antibiotic Max is the rare-tier gating step on top of it.
Brain true-ending route (and Overachiever unlock path)
The Brain true-ending route is the seven-biom run plan that ends with the Brain boss clear and the Overachiever unlock. Three guides specifically cover this route, and the truesteamachievements tracker names the Overachiever unlock as 0.5% Steam completion on AppID 3808690. ### Brain route overview The Brain route runs through all six main progression biomes (Skin, Intestines, Stomach, Liver, Lungs, Heart) in order, then enters the secret Brain biome. The 9puz.com Pathogenic Brain guide, the pathogenicgamewiki.com how-to-reach-the-brain guide, and the ingamenews.com best-parasites-for-reaching-the-Brain guide each walk through a parasite-selection step and an per-biome draft step. ### Parasite selection for the Brain route The cited guides converge on parasite picks that survive the high-density Lungs, Heart, and Brain biomes. The ingamenews.com guide is the media source for the parasite-selection framing; the allthings.how parasite tier list (Amoeba and Helminth as S-tier, Bacterium and lil collector as A-tier, Fungal Spore and Diatom as B-tier) is the comparative source. The /pathogen-roster selection-screen checklist covers the parasite pick step by step. ### Per-biome draft plan Each biome on the Brain route rewards a specific organelle draft and archetype commitment. The /boss-progression modules above (Skin, Intestines, Stomach, Liver, Lungs, Heart, Brain, Brain fight guide) walk through each biome's recommended organelle draft and archetype; the Brain route follows the same draft plan biome by biome. ### Overachiever unlock path The Overachiever achievement is the rarest achievement in the 41-achievement list on AppID 3808690 (0.5% Steam completion per the truesteamachievements tracker). The Overachiever unlock condition is Brain on antibiotic Max; this page records Overachiever as the Brain-route rare-tier gating step on top of the Brain clear. ### Heart-on-antibiotic-Max as a mid-route gating step The Heart-on-antibiotic-Max achievement (1.2% Steam completion per the truesteamachievements tracker) is the rare-tier gating step between the Heart clear and the Brain route. The 41-achievement list on AppID 3808690 also includes per-pathogen Heart-boss clears (beating the Heart boss with each of the seven pathogens), which means the Heart clear on a single parasite is the entry-level achievement and the Heart-on-antibiotic-Max is the mid-route gating step.
Sources
Sources checked 2026-09-01.
FAQ
How many bosses are there in Pathogenic?
Pathogenic has seven progression biomes and seven biome bosses: Skin, Intestines, Stomach, Liver, Lungs, Heart, and the secret Brain boss. The first six biomes are the main progression regions in the 1.0 launch build; the Brain biome is the secret progression region that gates the Overachiever achievement. The /boss-progression page walks through each boss's attack pattern, recommended organelle draft and archetype, gating unlocks, and matching Steam achievement. (Sourced from the Steam Hunters Pathogenic achievements list and the Steam store page for AppID 3808690.)
How do I reach the Brain in Pathogenic?
Three guides specifically cover how to reach the Brain: the 9puz.com Pathogenic Brain guide, the pathogenicgamewiki how-to-reach-the-brain guide, and the ingamenews best-parasites-for-reaching-the-Brain guide. The Brain route runs through all six main progression biomes (Skin, Intestines, Stomach, Liver, Lungs, Heart) in order, then enters the secret Brain biome; each biome on the route has a recommended organelle draft and archetype on the /boss-progression page. (Sourced from the 9puz Pathogenic Brain guide, the pathogenicgamewiki how-to-reach-the-brain guide, and the ingamenews best-parasites-for-reaching-the-Brain guide.)
What is the Heart boss cheese in Pathogenic?
The xmodhub Heart-boss guide documents the Heart boss's attack pattern and a specific cheese that the xmodhub page walks through step by step. The Heart boss is the sixth biome's survival check; the xmodhub guide frames the cheese as a defensive mutation layering on top of the committed archetype (ranged around Secretors or melee around Spikes and Flagella per the /builds page), not as a separate build. The /boss-progression Heart boss section is the canonical read for the cheese's role inside the run plan. (Sourced from the xmodhub how-to-beat-heart-boss-pathogenic-fast guide.)
What is the Overachiever achievement in Pathogenic?
Overachiever is the rarest achievement in the 41-achievement list on AppID 3808690, recorded at 0.5% Steam completion by the truesteamachievements tracker. The Overachiever unlock path runs through the Brain true ending; the cited Brain-route guides (9puz, pathogenicgamewiki how-to-reach-the-brain, ingamenews best-parasites-for-reaching-the-Brain) walk through the route but do not name the specific in-game unlock condition beyond completing the Brain route. Heart-on-antibiotic-Max (1.2% Steam completion per the same tracker) is the rare-tier gating step between the Heart clear and the Brain route. (Sourced from the truesteamachievements Pathogenic achievements page and the 41-achievement count on the Steam store page for AppID 3808690.)
Who is the final boss of the Brain in Pathogenic and what attacks does it use?
The final boss of the Brain in Pathogenic is Naegleria Fowleri, named in the pathogenicgamewiki Brain boss guide. The Brain boss uses a five-attack pattern of dash, ring, lightning, distortion field, and fungus traps; the wiki guide is the cited source for the attack names. The Brain fight is a boss rush that culminates in Naegleria Fowleri: the parasite refights earlier organ bosses in sequence, then reaches Naegleria Fowleri as the named final boss. The wiki guide is the source for the boss-rush framing, the attack names, and the named final boss. (Sourced from the pathogenicgamewiki Brain boss guide and the pathogenicgamewiki how-to-reach-the-brain guide.)
What build roles does the Brain boss in Pathogenic demand, and what is the Fungal Spore minion build that cleared it?
The pathogenicgamewiki Brain boss guide records five build roles the Brain boss demands: sustained single-target damage, repeatable non-kill Overcharge, invulnerability or shield, freeze control, and fallback damage. The wiki guide is the cited source for the role list. The same wiki guide records the Fungal Spore minion build that cleared the Brain as Nidublast + Apex Nidus + Pristine Mitochondrion + invulnerability + freeze + auto-charge. The wiki guide also lists six failure modes that wipe a Brain-route run: kill-triggered Overcharge, room-clear-only damage, pure melee, body-enlargement without mobility, no fallback, and glass cannons. Prep advice is to finish the build in the Heart before entering the Brain biome. (Sourced from the pathogenicgamewiki Brain boss guide.)