Characters / The Callisto Protocol

Jacob Lee

Jacob Lee

Voiced by: Josh Duhamel

The protagonist of the game, a cargo ship pilot whose ship crash-landed on Callisto, and was subsequently thrown into Black Iron Prison, before things really go wrong when the Biophage is unleashed.

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• Action Survivor: Jacob is a regular working joe, a cargo pilot running jobs for the United Jupiter Company. As a result, he has no real fighting skills and is forced to rely on the tools at his disposal in order to survive.
• The Atoner: Upon realizing the role he'd played in the attacks on the colonies.
• Character Development: Jacob develops in a subtle matter throughout the game. Under the influence of Elias, Dani and even Ferris and Mahler to a certain degree Jacob gradually accepts that all his choices have consequences and it is up to him to bear the responsibility for said consequences, dropping his Never My Fault outlook.
• Devoured by the Horde: The end of the Final Transmission DLC shows that the horde that attacked him at the end of the game managed to tear him apart, but his head and torso were alive and intact enough for Mahler to extract his memories and send them into space to hopefully corroborate Dani's claims against Ferris and his colleagues.
• Heroic Sacrifice: Puts Dani into the sole escape pod and sends her away from the self-destructing Black Iron as he stays behind. While the stinger at the end of the original game makes it look like he has a chance to survive, the Last Transmission DLC confirms his death at the end.
• Ink-Suit Actor: Looks very close to his voice actor in appearance.
• Miscarriage of Justice: The whole plot is motivated by Jacob being arrested and sent to B.I.P. for his presence at the crash site of the Charon, despite the fact that his only crime appeared to be (accidentally) crashing on Callisto. Later on, it seems clear that Jacob was arrested because he was complicit in smuggling the alien larva samples the UJC was secretly researching, even though he pointedly didn't want to know what was in the capsules to begin with.
• Never My Fault: An attitude that Jacob holds for a significant portion of the game, as he blames Dani for wrecking his ship and getting his co-pilot killed, when that was a direct response to him trying to kill her by blowing her and her comrades out an airlock. He also pretends ignorance of the role he was playing in the "attacks" on the various colonies, while his co-pilot had already connected the dots between the "attacks" and colonies they had visited. Once the full truth of what he'd been doing and what had been going on is made clear to him does he finally drop this attitude.
• Secret-Keeper: Jacob knew he and Max weren't just delivering medical caches to the colonies when he found one of the canisters holding the Biophage Pathogen (though he didn't know what it was) under the supplies. Instead of saying something when Max asks what he found, Jacob, who only cares about the big payout for their supply runs, brushes it off and says it's none of their business.
• You Are Number 6: Courtesy of Captain Ferris, who refers to Jacob exclusively by his prisoner number.

Max Barrow

Max Barrow

Voiced by: Jeff Schine

Jacob's partner and the co-pilot of their ship.

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• The Conscience: He was more worried about what he and Jacob had found in the medicine crate compared to Jacob. Downplayed, as he was not that insistent on calling Jacob out on it, seemingly not going beyond occasional passive-aggressive nagging.
• Facial Horror: The right side of his face is mutilated after the ship crash, with the lower half of his jaw hanging loosely from being severed.
• Family Man: A couple kid's drawings in his quarters show that he has a wife and child, which would compound Jacob's guilt over his death.
• Hallucinations: Under the influence of his CORE implant Jacob hallucinates Max at a few moments throughout the game.
• Morality Chain Beyond the Grave: He ends up playing this role for Jacob, because his hallucination's appearances aren't actually random. Instead, Max's apparition shows up every time the topic of Jacob's involvement in shipping the alien embryos comes up, with Jacob usually being in denial about his involvement. It is implied that it's actually Jacob's own repressed doubts and consciousness taking Max's shape in Jacob's mind, spurred by the CORE's influence.
• Sacrificial Lamb: He dies in the ship crash at the beginning of the game.
• We Hardly Knew Ye: The real Max gets very little screen time before sadly dying in the prologue.

Dani Nakamura

Dani Nakamura

Voiced by: Karen Fukuhara

A guerilla fighter opposed to the United Jupiter Company who finds herself captured and thrown into Black Iron, just like Jacob.

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• Action Girl: A member of an underground resistance movement, she's no less capable at dispatching monsters than Jacob is.
• Beauty Is Never Tarnished: Dani doesn't get her hair shaven off after her incarceration like Jacob does, nor does she get drenched in blood, dirt or sweat like him as they wade through Black Iron. Getting infected does tarnish her a bit, giving her a case of black Volcanic Veins and pale skin, but as soon as she is cured these go away without a trace.
• Defrosting Ice Queen: She starts off openly hostile to Jacob, believing him to be involved in the accident on Europa, but mellows out once she learns it's not the case. And even after she finds out he was actually involved after all she does not turn hateful again, having had a chance to know him better and witness his regret and desire to atone.
• Driven to Suicide: Almost goes through with it once she gets infected with the biophage, but Jacob stops her in time.
• Ink-Suit Actor: Like Jacob, Dani shares her appearance with her voice actress.
• The Lost Lenore: Her little sister Lily who died to biophages on Europa.
• The Scapegoat: For the Europa accident according to the UJC.
• Teeth-Clenched Teamwork: With Jacob at first. She might hate him but they both need each others' help to get off Callisto.

Leon Ferris

Leon Ferris

Voiced by: Sam Witwer

An unbalanced, sadistic prison guard captain at Black Iron and Warden Cole's right-hand man.

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• Bald of Evil: Downplayed, as his hair is shaved but only down to visible stubble, making him a bit resemble his voice actor's past role as Private Jessup from The Mist, though played straight after becoming a Biophage.
• Catchphrase: "There's always a price to pay", said when he flushes the airlock with Jacob and Elias inside, and then just after he goes One-Winged Angel.
• Cutscene Power to the Max: When Jacob sends a group of Biophages against him, he kills one with a single baton strike and another with a single GRP throw into a regular wall (rather than spikes or a Turbine Blender); Jacob can't One-Hit Kill Biophages like that even with max upgrades on easy difficulty. Also crosses into Cutscene Incompetence when the 3rd Biophage seemingly kills him with a single tackle over a ledge.
• The Dragon: Warden Cole's right-hand man. He continues this role even after transforming into a Biophage, thanks to managing to retain his intelligence and humanity.
• Establishing Character Moment: His introductory scene shows him being flippant of Max's death, then having Jacob and Dani detained per the Warden's orders (which he follows without question). From there, Ferris addresses both Jacob and Dani as inmates and explains to them that their lives are now his to control, with a not-so-subtle threat of using his Gravity Restraint Projector on Jacob, showing how much he revels in his power and enjoys lording it over everyone else.
• Faux Affably Evil: Once Jacob is in his clutches and is about to be processed Ferris offers him some words of consolation that are filled with condescension and veiled threats. Later his reaction to Dani getting infected is an "Oh no" that is simply dripping with sarcasm.
• Ink-Suit Actor: As with Jacob and Dani, Ferris bears a striking resemblance to his voice actor, especially taking after his character Private Wayne Jessup in some fashion from The Mist due to their shaved heads.
• No-Holds-Barred Beatdown: If he gets ahold of you, he'll absolutely pummel Jacob's head in. Oh, and he'll spit on your corpse afterward.
• Punch-Clock Villain:
  • While he is certainly an ass, he never goes out of his way to Kick the Dog, and is willing to be friendly with Jacob until the warden requests he be detained. He only really starts getting aggressive with Lee after things have gone to hell, and considering how Jacob sent a pack of biophages at him as a distraction, this is understandable.
  • He's also not a member of Kallipolis/The Circle, unlike Warden Cole or Dr. Mahler, and is caught completely unaware just like the rest of the guards when Cole activates the Callisto Protocol.
• Pre-Asskicking One-Liner: Delivers one in the final fight
  "Now, I'm gonna show you"

• Sociopathic Soldier: In the past - his profile mentions a history of service in the special forces and multiple disciplinary infractions on his record.
• Soft-Spoken Sadist: He never gets physically abusive with Jacob until the shit hits the fan, but it's clear from his demeanour before and after the outbreak starts that he enjoys lording over his prisoners as an overseer.
• Villainous Valor: To his credit, when Jacob sends a few Biophages headed his way, Ferris takes them head on.

Elias Porter

Elias Porter

Voiced by: Zeke Alton

A longtime inmate at Black Iron who aids Jacob in his escape.

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• The Atoner: Despite having mitigating circumstances to his crimes and wanting to break out of the Hellhole Prison he's stuck in, he does believe that he still needs to make up for what he's done. It's indicated to be why he's so friendly, helpful and generally pleasant to be around.
• Crazy-Prepared: The only reason Jacob (and later, Dani) get as far as they do is due to his machinations, as he'd been planning to bust out for years and put "caches" of information and supplies in place to help down the line. As Jacob is travelling through the Biodome, Elias' previously downloaded codes to Jacob's CORE device allow him to access holographic memories of Elias explaining his plans/objectives out loud so that he (and anyone working with him) will know what to do and where to go.
• Crime of Self-Defense: From what little he says about his past, it's implied he made a lot of bad choices in life and eventually ended up the winner of a kill-or-be-killed situation which didn't fall under self-defense (such as a gang shootout or killing an armed homeowner), or at least not under circumstances the authorities would be sympathetic to. Elias takes full responsibility for his actions and refuses to blame anyone but himself for his situation.
• Dark and Troubled Past: Admits to having made a lot of bad choices both during and prior to his time at Black Iron. When Jacob asks him what his crime was, Elias straight out admits to being a murderer and takes full responsibility for his actions.
• I Die Free: In his last moments he takes solace in the fact he's not dying inside the Hellhole Prison he's spent half his life in, but rather outside it, having successfully escaped.
• Mission Control: He's Jacob's only support in the first half of the game, being the one prisoner who knows the prison and is able to execute on his plan by guiding Jacob to various locations so that they can both escape.
• Nice Guy: Friendly, considerate, and extremely helpful. It's indicated to be a deliberate way of being The Atoner for his past crimes.
• The Old Convict: Has spent half of his life in Black Iron and knows it almost like the back of his hand.
• Sheep in Sheep's Clothing: He comes across as oddly friendly and helpful for an inmate in a maximum-security prison, even taking into account the alien Zombie Apocalypse that's forcing him and Jacob to work together to survive. Not only that, but there's a string of odd coincidences as you follow his instructions that make Jacob (and potentially the player) begin to suspect that he's just using him as a disposable patsy to help with his own escape. None of it is true, though - he's The Atoner and a sincere Nice Guy who's doing his best in a difficult, chaotic situation.
• Voice with an Internet Connection: Most of the time he's away from Jacob, talking to him via their implants and guiding him through Black Iron, as he's often in a better position to access its computer systems.

Duncan Cole

Duncan Cole

Voiced by: James C. Mathis III

The Warden of Black Iron prison.

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• Affably Evil: He is nothing but perfectly polite and even cordial with Jacob, offering him his sincere respect once Jacob earns it in Cole's eyes.
• Ancient Conspiracy: Is a part of one called Kallipolis (who have the same logo, motto, and ultimate goal as the Ancient Conspiracy from Player Unknowns Battlegrounds), which has been trying to guide humanity's development for centuries and whose ultimate goal is to create "The Commonality", the next step in human evolution.
• Bald of Authority: He has a smooth shaved head and is the ultimate authority on Callisto. Also doubles as Bald of Evil.
• Big Bad: He's the man in control of the Hellhole Prison Jacob and his allies are trying to escape from, and turns out to be responsible for causing the Biophage outbreak.
• Canned Orders over Loudspeaker: Black Iron is peppered with his prerecorded holographic addresses to prisoners. Which is played for a minor spook once, when a hologram turns out to be a direct message to Jacob instead.
• Even Evil Has Standards: Inverted, in that Cole is the one who has less standards compared to other evil characters. Both Mahler and his fellow Circle members think he's going too far in his methods.
• Evilutionary Biologist: Cole seeks a way to improve humanity's physical form, and sees the biophage as a potential way to do this. For this reason he causes the biophage outbreak in Black Iron in order to find his Alpha, because "evolution does not happen in the lab" (notably, Mahler, who is an actual scientist, scoffs at this viewpoint). He also believes in the evolution as "survival of the fittest", which is why he wants Jacob alive as the exemplar of humanity's will to survival, in order to have him fight his Alpha and through that find out which form is superior.
• I Want Them Alive!: Cole wants Jacob captured alive once he sees him as the perfect manifestation of mankind's survival instincts. Sadly, his Alpha does not care, and both times you fight him it's to the death.
• The Unfought: He's only ever encountered as a hologram. Even at the end of the game when it seems you're confronting the real Warden, he turns out to still be a hologram (just a more realistic appearing one) when Dani tries to just shoot him in a Shut Up, Hannibal! moment.
• Villain Has a Point: While he is wrong about a lot of things, he isn't wrong about the Biophage having a legitimate advantage when it comes to surviving hostile environments, as the Biophage can easily survive on Callisto's surface despite the lethal atmosphere and freezing temperatures, something that would quickly be fatal to ordinary humans.
• Visionary Villain: He's driven by his vision of evolving mankind into a superior more robust form.
• Well-Intentioned Extremist: Despite his terrible actions, including causing the biophage outbreak, he does have genuinely good intentions. He honestly believes that the only way humanity can survive outer space is by forced evolution to make themselves strong enough to endure harsher environments.

Caitlyn Mahler

Dr. Caitlyn Mahler

Voiced by: Louise Barnes

The Chief Medical Officer of Black Iron Prison.

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• The Atoner: In the present. Seeing how far Cole is willing to take the biophage project, she decides she's had enough and turns against him, helping Jacob behind Cole's back.
• Chekhov's Gunman: She briefly appears during the prologue to forcefully outfit Jacob with his CORE implant and vanish for most of the game save for prerecorded logs, only to reappear almost at the end for a crucial part.
• Face Death with Dignity: After sending Lee's memories into space to help Dani take down Cole and Kallipolis, she seems at peace and makes no effort to try and escape Black Iron, only looking upwards as the ceiling finally collapses upon her.
• Heel Realisation: Has one after hearing how Cole considers the Europa outbreak a revelation and an opportunity.
• For Science!: Her original motivation. in her recordings she gleefully speaks of wonders and potential applications of the biophage pathogen to enhance the humanity, and she doesn't mind conducting experiments on living humans to unlock those applications.
• A Lighter Shade of Black: Compared to Cole. She's still an amoral scientist who experimented on humans and had possibly knowingly sent another science team to their deaths to survey the old colony, but unlike Cole she considers the Europa outbreak nothing but a tragedy, and turns against him after he replicates it in Black Iron.
• Morally Ambiguous Doctorate: She outfits Jacob with the CORE implant after he has been unlawfully incarcerated at the start of the game without batting an eye, and that's just the tip of the iceberg.

Biophage

An alien virus converted by humans that transforms the human body into a biological nightmare.

In General

• Admiring the Abomination: The Circle desperately wants to use the Biophage in order to evolve humanity. They admire the resilience and strength of their subjects seeing them as progress despite the obvious murder.
• The Berserker: How most attack in general. Very few tend to apply strategy when faced with Jacob or other individuals.
• Body Horror: Much like their inspiration, the Biophage transforms humans into grotesque amalgamations. Most do seem human from a distance but get more gruesome the closer you inspect.
• Came Back Wrong: Due to the nature of the Biophage the individuals no longer resemble their previous selves. In some cases they don’t even resemble the same species.
• Eldritch Abomination: In Final Transmission an audio log from Mahler speculates [[spoiller:that the Biophage is a single intelligent entity and older than the known universe]]. Exactly what caused her to reach this conclusion is not overtly stated.
• The Heavy: Collectively, they're the main obstacle Jacob must wade through to escape Black Iron, with Warden Cole being the architect behind the outbreak.
• Hive Mind: Its not stated outright but there are hints that biophage creatures operate under one. A few logs left by people in the early stages of infection (as well as Dani) mention how they can feel a foreign presence inside of their minds. There's also Subject Zero's inexplicable ability to control other biophages, which could be explained via him being the leader of their hive mind.
• Humanoid Abomination: This is absolutely true due to the intent of the virus. Mutating human genes to undergo a surge of strength but twisting the body into a mass of muscle and viscera.
• It Can Think: Certain members tend to understand the melee variations and can occupy Jacob while others sit back and take shots from afar. It’s also common for them to ambush the player. Also, if you try to funnel a group of Biophages into a narrow space to try and fight them one at a time, the front Biophage will often just grab you and throw you so you end up in the middle of the entire group where they can all attack you from every direction.
• Immune to Bullets: A good number of them are bullet sponges but not inherently immune. However much of this comes from your overall lack of ammo and the fact for much of the game your guns tend to be on the smaller side (a pistol and a homemade sawed-off showgun). Unload on them with an assault rifle and they go down after about the same amount of lead as enemies in many other video games.
• Losing Your Head: Some can survive decapitation and will not react much if you inflict it on them.
• Made of Iron: Many of the mutants don’t even flinch if you shoot them.
• Nightmare Face: All of them. Due to the unstable nature of The Virus their bodies are malformed around the faces, especially the Corruptor. The exceptions are the Alpha during its earlier phases and the Larvae due their faceless nature.
• Our Zombies Are Different: The Biophage are disturbingly intelligent and tactical, capable of blocking melee attacks, sneaking through ventilation ducts, playing dead to ambush victims, and utilizing pack hunting techniques. Rather then biting and eating their victims they prefer slow, deliberate methods of execution, such as gouging eyes, ripping limbs off, or stomping both arms of their victim into paste, leaving them screaming in agony before a finishing blow to the head. The Alpha instances even retain their full intellect and humanity, such as Captain Ferris and Subject Zero.
• Super-Strength: The Virus mutants the human body the peak condition which allows them to achieve peak physical strength. Most are able to kill Jacob rather easily.

Grunt

The basic biophage mutants encountered in the game. They can mutate to become stronger but otherwise have no distinguishable features.

• Didn't Need Those Anyway!: Losing their limbs does nothing to deter them, and they will keep attacking Jacob even without both arms.
• The Goomba: Early on, standard Grunts have reduced health and can't mutate. After the first few chapters once you get a full equipment loadout, the Grunts become tougher and start being more on par with other Biophage types in terms of durability.
• Hulking Out: After the first couple of chapters, Grunts gain the ability to mutate into a larger, stronger form (and restored to full health) after they've taken damage. This is indicated by tentacles bursting out of their chest, which can be shot to kill them and prevent the mutation.
• Stout Strength: The fat inmate mutants have more health and are better at blocking than the regular inmate ones.
• Was Once a Man: All rabid biophages were once inmates or security personnel of Black Iron.

Big Mouth

A mutated human that carries the Biophage and continues to transmit it to other viable hosts. It is the only biophage creature that can attack at range.

• Cthulhumanoid: It has rather small but noticeable tentacles where its mouth once was.
• Breath Weapon: It vomits the virus out of its mouth. Both at long range and close range.
• Elite Mooks: They're a step up from the fat mutants and mutated security guards, and are the largest and toughest Biophage enemies you'll face in the first half of the game.
• Expy: Of both the Spitter Necromorph and the Infector. As it transmits the disease and spits globs at Jacob.
• Foreshadowing: Their heads seem to be splitting apart into two seperate ones, which foreshadows the two-headed Boss in Mook's Clothing enemies that show up in the last few levels of the game.
• Hero-Tracking Failure: Despite Jacob's movement speed being best described as "glacial", you can still evade their spit attacks as long as you're strafing sideways whenever they spit.
• Hulking Out: Like Grunts, after the first couple of chapters they can mutate into a stronger form after taking damage, unless you shoot the tentacles that burst from their mouth just before this happens.

Larva

Strange, grub-like creatures that often attack the player when opening containers.

• Chest Monster: They are never encountered in the open, but frequently ambush Jacob from inside lockers or chests.
• Gameplay and Story Integration: Their tendency to show up and attack out of nowhere isn't isolated to just Jacob, as they infect Dani with the virus during an unexpected surprise attack.
  • Gameplay and Story Segregation: Of course, they very conveniently jump at Jacob's shoulder first instead of going for his face like they do Dani, allowing Jacob to remain uninfected during the course of the game.
• Jump Scare: Their primary tactic, they'll often jump out of containers to attack the player and force them into a quick time event.
• Orifice Invasion: If you fail to shake them off in time they will infect Jacob and kill him - by physically crawling into his mouth and throat.
• Small Role, Big Impact: They're the primary vector of infection, the larvae of an alien creature that carry the Biophage virus. As such, they're the reason why the outbreak is happening at all.

Bloodworm

A long-necked creature hiding inside biophages eggs, attacking anyone who gets too close. Like Jacob.

• Ambushing Enemy: They can sometimes hide inside biophages eggs, with eggs containing them visually indistinguishable from "safe" eggs. You can shoot eggs from a distance to prevent them from emerging if you don't want to deal with these things, but that requires wasting precious ammo.
• Body Horror: The "worms" are seemingly made of mutated human skulls, attached to their eggs via an extremely long spine. No limbs or organs to speak of remain.
• Press X to Not Die: Once they spring out and attack Jacob you become engaged in a simple QTE to shake them off. If you fail, they will drag Jacob to the egg and bite his head off.

Combustor

A crawling biophage creature covered in caustic pustules.

• Action Bomb: They blow up when killed, and will try to kill Jacob by crawling up to him and exploding next to him.
• Expy: Of the Exploder Necromorph from Dead Space, fulfilling the same role

Corruptor

A larger, crawling quadruped biophage creature seemingly consisting of multiple human bodies melded together into a single organism. Unlike most other mobile biophages they prefer ambushes to direct attacks.

• Ceiling Cling: They can move across walls and ceilings just as easily as they do over the floor.
• Elite Mooks: A group of them is first encountered as a boss fight in the sewage control room, but later you start running into them on a more regular basis.
• Expy: They are very similar to the Stalkers from Dead Space 2, frequently lurking out of or in brief view before they attempt to tackle you and retreat to cover for another round.
• Glass Cannon: Their health is average (though the fact they run away alot means landing consecutive melee strikes on them is very difficult), but they hit hard and can take off well over half your total health in just 1 hit.
• Hit-and-Run Tactics: While most Biophages are melee berserkers limited to Attack! Attack! Attack!, these guys use hit-and-run tactics instead, pouncing on you then quickly retreating into vents or the ceiling.
• Invisibility: Dr. Mahler's audio log on them indicates they can turn invisible, although (not including ones that pounce on you from off-screen in semi-scripted events) you only run into one that does so, very near the end of the game.
• Non-Indicative Name: Based on their name you'd think they'd be able to convert humans into Biophages, similar to the Infectors from Dead Space. Nope, it's the Big Mouths that do that. Based on the areas you encounter them in, the Corruptors seem to be responsible for creating the Meat Moss in Biophage-infected areas, corrupting the environment, a fact which is vaguely referred to in Dr. Mahler's audio log on them.

The Blind

An old strain of biophages encountered on deep levels below Black Iron. Spending a long time in the darkness they have adapted to it, navigating their surroundings by hearing but completely losing their sight in the process.

• Achilles' Heel: Their blindness. They will fail to notice Jacob even if he is standing right in front of them as long as he's not making any noise, and while they are very dangerous in the open combat they can still die to a single stealth takedown. Also, you can pick them off one-by-one with the GRP's telekinesis without alerting them.
• Berserk Button: You can use telekinesis or get into a melee fight in a Blind-infested area and not be swarmed, as they only respond to most noises if you're within several feet of them. However, if you fire a gun, every Blind in the area (which can be up to almost a dozen) will immediately aggro and swarm you, which can often be an unwinnable fight.
• Elite Mooks: They hit very hard and are extremely resilient themselves. Engaging them in a straight fight is more trouble than it's worth, especially given they tend to appear in large groups, so it's better to sneak around them.
• Evil Evolves: They've become what they are after spending decades in hibernation under the surface of Callisto, adapting to its darkness.
• Hulking Out: They share the Grunts' ability to mutate into a stronger form after taking damage.
• Was Once a Man: Like all other biophages, except they don't come from Black Iron but rather from an old colony of Arcas, which had discovered the biophage infection decades ago, and on top of which Black Iron was built.

Two-Headed Brute

An especially strong biophage variant, looking like a humanoid body with two torsos and heads.

• Contractual Boss Immunity: He's too large to be GRP'd, and you can't do melee combos on him as he won't be staggered and will just clobber you after the first hit. He also can't be stealth-killed.
• Degraded Boss: The first time you meet one it is preceded by a cutscene and it is dealt with in a one-on-one fight. The second one also has a cutscene but it's shorter and in its fight it is supported by regular grunts. Your third and fourth encounter with the Two-Head have no fanfare at all.
• Didn't Need Those Anyway!: As its health gets depleted you will actually blast off one of its torsos along with the attached arm and head. It still remains dangerous and can kill you even in this weakened state.
• Giant Mook: It is the biggest biophage creature except for the Final Boss, towering over Jacob and with a bulk to match. It attacks with single, heavy swings, which deal heavy damage if they connect.

Subject Zero (Unmarked Spoilers)

A human man who lived in the Arcas colony when the first biophage outbreak hit it. Unlike all other colonists he retained his intelligence post-infection and gained tremendous strength and powers from it, far exceeding that of other infected over whom he also had control. He was killed when the military came in to suppress the outbreak.

• Cool, but Inefficient: He had gained superhuman biological powers from the biophage infection, but they still didn't save him from being taken down by mundane guns when the military arrived. His fate could be considered Foreshadowing to that of the Final Boss.
• Dead Guy on Display: His remains are held suspended in the center of a circular frame right in the middle of a laboratory.
• Living Macguffin: Formerly living. The Circle and Warden Cole still view him and his remains as the key to their goal of improving humanity.
• Monster Lord: He was able to control other mindless biophages around him.
• No Name Given: Current holders of his remains didn't seem to bother to record or remember his name, and he's only ever referred to as Subject Zero.
• Posthumous Character: He's been dead for decades, but still plays an important part in plans and motivations of the Big Bad.
• Superpower Lottery: Through a quirk in his genetics he had retained his intelligence and got an even bigger power boost than normal following his biophage infection.

Subject Alpha (Unmarked Spoilers)

Leon Ferris

Seemingly dying when swarmed and tackled by biophages out of his control tower's window, Captain Ferris actually survives and gets infected - but instead of turning into a mindless brute like all the rest he retains his human intellect and gains an even stronger array of powers. This puts him right in the center of Warden Cole's plans as his Subject Alpha - the successfull attempt to replicate Subject Zero and a possible lead to using the biophage to enhance humanity.

• Attack Its Weakpoint: In his final form Ferris is only vulnerable on his head.
• Body Horror: As his mutation progresses his skin turns corpsy-pale with Volcanic Veins and he gains a distorted deep voice. Then his second stage of mutation triggers, when he turns into a misshapen hulking vaguely humanoid mountain of twisted flesh. His fingertips, just to give one example, end with what seems like miniature hands with fingers of their own.
• Contractual Boss Immunity: In his first form he's immune to the GRP as well as to the block-breaker and counter-attack upgrades to the stun baton. In his final form he's too large to be engaged in melee at all, and must be taken out with firearms.
• Cool, but Inefficient: Same as Subject Zero. Ferris, touted as a superhuman and the next step in the human evolution, jacked up by biophage into a gigantic inhuman monstrocity, still loses to a space trucker with a gun.
• Drunk with Power: Once he settles into his infection Ferris savours his transformation and new power. It's especially pronounced in his second fight with Jacob where he openly brags how he's stronger than anyone.
• Final Boss: He serves as the ultimate opponent of the game.
• Flunky Boss: Ferris' final form isn't too overwhelming (his melee strike, while extremely powerful, can be dodged just like any other, and his projectile attacks don't do too much damage and can also be avoided), but the big challenge in the fight comes from the fact that constantly respawning Combustors will keep trying to suicide bomb you while you're busying fighting him.
• Good Old Fisticuffs: He forgoes any weapons when dealing with Jacob in his first form, just trying to beat him to death with his bare fists. If you're not careful that can be all he needs.
• Immune to Bullets: Played straight in his first form. Jacob's ranged attacks only briefly daze him at best, but mostly just piss him off. This extends to gameplay as well; he isn't staggered by gunfire like regular Biophages are, and he's also extremely resistant to bullet damage, requiring over 100 rounds of fully upgraded assault rifle fire to end the fight both times you fight him (whereas if you stick to melee attacks he's only got about 2 to 3 times the health of a regular Biophage). Even in his second form (which can only be defeated with firearms or explosives) only his head is vulnerable, and he covers it with a fleshy armor dome that needs to be shot off.
• Jump Scare: The game ends with his snarling face lunging at Jacob through Mahler's hologram, implying that he may be Not Quite Dead.
• King Mook: In his first form, he has a few unique advantages (besides the Contractual Boss Immunity and Immune to Bullets already mentioned, he also has a really long combo string of several punches instead of just 2 or 3 like other Biophages), but otherwise fighting him is just like fighting any other Biophage in melee combat.
• Living Macguffin: As the Alpha Ferris is this both to Cole and to Jacob. For Cole, he is the next step in the human evolution he was looking for, and Jacob needs a sample of his tissue in order to stop Dani's biophage infestation.
• No One Could Survive That!: After Ferris gets tackled through the control tower's window Jacob assumes that that is the end of him. He assumes wrongly.
• One-Hit Kill: On normal difficulty, a punch from his final form will splatter Jacob into chunks even if he's at full health.
• Playing with Fire: Gains incendiary attacks in his final form.
• Recurring Boss: Jacob fights him twice throughout the game, barely escaping after the first time but defeating him in the second.
• Superpower Lottery: Like Subject Zero, Ferris lucks out and only gets stronger from the biophage with no drawbacks. At least, at first.
• Superpower Meltdown: Halfway into his second fight with Jacob his mutation goes out of control, turning his almost unchanged human body into a towering horror of flesh.
• Villainous Valor: Again, to his credit, he takes his second transformation with surprising dignity, only saying "there is always a price to pay" as he turns into a monster.

Biobot

A new enemy that appears in the "Final Transmission" DLC. Appears to be a Security Robot that has had many of its parts replaced with biophage-infected organic components.

• And I Must Scream: The data logs you find indicate that by integrating the infected subjects into a security robot, Mahler was partially successful in averting the homicidal insanity of biophage transformation. However, being turned into a cyborg and with no clear purpose in life remaining, the subjects would grow increasingly insane and aggressive anyway. This is a foreshadowing of Jacob's own situation as human remains hooked up to a life support machine; Mahler is having him go through "one last mission" in his mind to help maintain his sanity while she transmits her data through his brain chip.
• Area of Effect: They can overcharge and release a burst of electricity, damaging you if you're standing too close. This attack can be blocked, but only if you're not committed to a combo chain. This both makes the block move somewhat useful (there was no point using it in the main game) and also encourages the player to not just mash the attack button during the fight.
• Degraded Boss: The first two you encounter are treated like Mini-Boss battles; the first you're encouraged to stealth around, while the second one is a mandatory fight and also has more health than normal. Later in the game you encounter them in larger numbers and have to find a kinetic hammer to be able to fight them in groups.
• Meat-Sack Robot: The data logs you find indicate they're biophage-infected subjects integrated into a security robot chassis.
• Stone Wall: They can take a lot of hits, having several times as much health as a regular Grunt and requiring over 40 rounds of fully upgraded assault rifle fire to bring down. They can also be very fast when they want to, but surprisingly their attacks don't do much damage despite how huge and powerful they appear.

The Final Biophage (Unmarked Spoilers)

Dr. Caitlyn Mahler

A Biophage-mutated Dr. Mahler serves as the Final Boss of the Final Transmission DLC and the Callisto Protocol storyline as a whole, transforming into a powerful and unique Biophage mutant after being infected and thrown down a garbage incinerator by one of the Biobots. Jacob Lee fights her in one final battle before finally departing Callisto once and for all.

• All Your Powers Combined: She has the size and raw strength of the Two-Head combined with a spit attack similar to the Big Mouth's.
• Attack Its Weak Point: When in her ranged combat mode, she'll have a glowing red weak spot in her open chest which is the only means of damaging her.
• Combo Breaker: She has an undodgeable ground slam attack to break your combat flow, so you can't always just wait to dodge her attacks then counterattack and will have to be aggressive at some points in melee.
• Contractual Boss Immunity: Like the Two-Head and Ferris, she can't be GRP'd.
• Final-Exam Boss: Defeating her involves a mix of melee and ranged combat, as she uses both melee and ranged attacks and is only vulnerable to melee damage when in melee mode and ranged damage when in ranged mode. Additionally, she has an undodgeable ground slam attack, which forces you to be aggressive at some points in melee and not just rely on the usual dodge-counterattack crutch you've used the entire game. Saw blades and explosive cannisters are also scattered around the arena which can be thrown at her with the GRP to damage her in either mode.
• Giant Space Flea from Nowhere: She has no plot-related reason to mutate into a giant super-Biophage, and her doing so is All Just a Dream anyway, so she seems to just exist to close out the series on a Final-Exam Boss fight that seems designed to encompass the game's whole combat system better than the Ferris boss fight from the end of the main game.
• Teleport Spam: She'll teleport around between spit attacks in her ranged combat mode, exhibiting an ability which breaks the laws of physics much more than anything else demonstrated by any other Biophage. This is a hint that the events of the DLC are All Just a Dream.

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