Dead Space Wiki

"I hear it too, Mr Harris. Others find the Marker's signal a burden, but for me it's... inspiring. New surgical techniques, new technical designs... A pity I can't grasp the deeper nuances like you do. [...] You have divine insight, Mr Harris. I can interpret it. The deepest secrets of the Marker - Convergence, even the Hive Mind itself - could be ours. If you trust me."
—Dr. Mercer to Brant Harris.[1]

Doctor Challus Mercer was the Second Science Officer[2] aboard the USG Ishimura and a devout Unitologist to the point of zealotry.

Mercer became fanatically obsessed with Marker 3A and the Necromorphs after the Ishimura was compromised, believing that Convergence was the gateway to life after death.



Challus Mercer was one of the numerous Unitologists aboard the USG Ishimura, presumably introduced in the massive turnover caused by the Church of Unitology to grant Captain Mathius a majority of devouts composing the crew. Logs left by Mercer[3] as well as comments from Dr. Terrence Kyne[4] indicated that Mercer possibly became a believer due to his fear of death and his deep desire to transcend it through Convergence.

While unconfirmed, it is quite possible that Challus Mercer was a high-ranking member of the Church of Unitology before joining the USG Ishimura, as he could be heard delivering speeches to his fellow Unitologists on the Crew Deck, asking them not to abandon their faith despite the appearance of the Necromorphs.

The Second Aegis VII Incident[]

"Convergence. Where the bodies of the dead will rise; united, undying, made whole by the Marker. So we're taught. But all this raw material, all my work, and the Marker remains inert. Ever since that... first contact, as it were, words repeat in my head: "the makers must be absorbed." A divine insight, perhaps, that creating my hunter is part of the answer..."
—Mercer in his personal journal.[3]
DSR Harris ICU

Mercer experiments on Brant Harris to unlock the Marker's secrets in his mind.

Mercer was one of the medical officers to study the Aegis VII colonists suffering from dementia and was especially interested in the miner Brant Harris' ramblings, considering them "religiously significant". During a conversation with Harris, he revealed that he gained knowledge from Marker 3A's signal, similar to those individuals who would receive Marker blueprints. However, the knowledge Mercer received was instead new surgical techniques and new technical designs, which he used to perform his experiments. Mercer interrogated Harris to find out the "deeper nuances" of the Marker, but Harris told him that every time he tried to give that information to him, it slipped away from his mind, almost like it was "stuck behind [his] eyes". Mercer then devised a possible solution to this problem, injecting Necromorph biomatter into Harris' brain in the hopes of unlocking the Marker-affected parts of his mind and discovering a way to "speak" to the Marker.[1]

During the outbreak, Mercer tried desperately to make the Marker initiate a Convergence Event, intending to transcend death and finally be "made whole". After his experiment with Harris, Mercer was finally able to devise a way to communicate with the Marker, asking it about Convergence. When the Marker told the doctor that "the makers must be absorbed" to achieve Convergence, Mercer took this answer to mean that he must create new forms of Necromorphs, eventually leading him to create his "Hunter" from Harris' body.[3] Mercer began to research the creatures extensively, using his prototype Stasis Module to safely capture and study them.[5]

Arrival of Isaac Clarke[]

"Try and relax, Mr Clarke. Convergence is so close. Maybe your death will tip the balance."
—Mercer to Isaac Clarke.
DSR Mercer Unleashes Hunter

Mercer decides to unleash the Hunter on Isaac Clarke.

Mercer also set up a false transmission asking for survivors to come to Medical using a recording of Dr. Nicole Brennan. This attracted the engineer Isaac Clarke, whom Mercer recognized as Nicole's boyfriend. After a brief confrontation in which Mercer asked Isaac if Nicole's "meddling" was the reason the Marker still had not begun Convergence - referring to Nicole's earlier act of stealing research on the Marker from his hideout[6] - Mercer unleashed the Hunter on Isaac, telling him that he intended to find out if death by dismemberment was the "missing factor" for Convergence.[7]

DSR Marker Mercer Unitologists Prayer

Mercer leads a group of Unitologists in prayer in front of the Marker.

After Mercer and several other Unitologists brought the Marker from the cargo bay to the Crew Deck, the doctor appeared to have become the leader of the surviving believers on the ship, conducting sermons and delivering speeches as they awaited Convergence. Eventually, Mercer lured the engineer Jacob Temple to the Crew Deck through a distress call, capturing him and forcing him to help with the Unitologist's experiments. Temple mentioned in an audio log to his girlfriend Elizabeth Cross that Mercer was forcing him to "build something to make his Marker start... converging?",[8] indicating that Mercer was still trying to find ways to fulfill the Marker's request, fruitlessly attempting to have Temple become a "maker" for the artifact.

DSR Mercer Make us Whole

Mercer begs the Marker to bring Convergence, to no avail.

After Isaac Clarke incinerated the Hunter with the Executive Shuttle's engines, Mercer checked up on the creature to see that it had been completely obliterated. Seeing Isaac struggling against a giant tentacle that was about to drag him off to the ship's vents, Mercer raged and insulted the engineer for destroying his work, before turning to the Marker and begging it to "take" Isaac and begin the Convergence Event right away, to no avail. Instead, another massive tentacle wrapped itself around the Marker and dragged it and Mercer down to the cargo hold, crushing the doctor against the Marker and killing him in the process.

Personality and Traits[]

"Friends, do not trouble yourselves with the words of the heretic Kyne. The Marker stands ready. Convergence is imminent. Don't fear the process of transformation. Or the appearance of these holy creatures. Angels, too, seemed monstrous to the unprepared. A moment's pain will fuel humanity's ascension. Do not falter on the very brink of transcendence."
—Mercer convincing the surviving Unitologists to give themselves up to the Necromorphs.
DSR Mercer Room Concept

Mercer's office during the Necromorph outbreak.

Prior to the outbreak, Mercer was a hardworking crew member aboard the USG Ishimura, described as a "charming Unitologist with many talents".[2] According to Terrence Kyne and Nicole Brennan, however, his methods were often objectionable and dangerous, and when word of the dementia affecting the colonists on Aegis VII reached the Ishimura staff, Mercer clashed with Kyne over how they should study the situation, with Kyne losing his faith in Unitology due to believing the madness was connected to the Marker, while Mercer saw the artifact's effects on the colonists' minds as proof of its divinity.[9] After the Necromorph outbreak began, Mercer attempted to aid the creatures in their assault on the ship, believing that they were sent by God to bring about Convergence.

Kyne stated to Nicole that the only thing Mercer ever feared was death;[4] it was because of this fear that Mercer desperately attempted to make the Marker initiate a Convergence Event. However, he began growing frustrated as the Marker gave no signs of initiating Convergence despite the amount of Necromorph biomass at its disposal. Mercer's subsequent predatory behavior, luring victims to experiment on and create new forms of Necromorphs, was the doctor's way of fulfilling the Marker's request that "the makers must be absorbed" for Convergence to take place.[3]

DSR Slow Death in Stasis

Mercer kills Jacob Temple after immobilizing him with Stasis.

Mercer believed that greatness could never be achieved by conventional means and appeared to have an arrogant view of Unitology, deluding himself into thinking that he had personally been "promised" Convergence and thus not being willing to become a Necromorph himself despite viewing the creatures as "holy". After his efforts to have the engineer Jacob Temple become a "maker" for the Marker failed, Mercer launched a last-ditch attempt to fuel Convergence by delivering speeches to the remaining Unitologists, urging them not to fear the Necromorphs and to give themselves up to the creatures, even going so far as to release poisonous gas to kill those who could not bring themselves to do so.[10]


  • Pakistani-American actor Faran Tahir provides the voice and likeness of Mercer in the 2023 remake.[11] In the original game, Mercer was portrayed by Iranian-American actor Navid Negahban.
  • Mercer's experiment of attempting to unlock the Marker knowledge in Brant Harris' mind - inserting a sample of Necromorph tissue through his ocular cavity and into the right region of the brain - was a process very similar to what would later be used by EarthGov for Project Telomere with the Noonlight Diagnostics Machine, though the latter did not involve Necromorph material.
  • During the scene where Mercer leads a group of Unitologists in prayer at the base of the Marker in the remake, he and his followers seem to be chanting "Sumus hic in morte; noster sanctus est" ("We are here in death; it is our saint"), the same Latin chant that the Marker emits in both the original game and the remake.[12][13]



"Am I the only one who sees that we have died out a long time ago? We just haven't accepted it yet. Stop running. Stop your struggle. Our future, your future, the future of our race, ends here! Allow me to introduce you to humanity's child. The children that will replace us! Our greatest creation."
—Dr. Mercer introducing Isaac Clarke to the Hunter.

Doctor Challus Mercer was the Second Science Officer[1] aboard the USG Ishimura and a devout Unitologist to the point of zealotry.

Mercer became fanatically obsessed with the Necromorphs after the Ishimura was compromised and the infection spread. Mercer believed that the Necromorph infection was the next stage of the human race and their ability to reanimate necrotic flesh was life after death.



Challus Mercer was one of the numerous Unitologists aboard the USG Ishimura, presumably introduced in the massive turnover caused by the Church of Unitology to grant Captain Mathius a majority of devouts composing the crew.

While unconfirmed, it is quite possible that Challus Mercer was a high-ranking member of the Church of Unitology before joining the USG Ishimura; a large Marker ornament could be found on a table near the place of his death on the Crew Deck. Furthermore, there was a recording of him making a speech to fellow Unitologists next to this ornament, asking them not to abandon their faith despite the current outcomes of the extraction mission.

The Second Aegis VII Incident[]

Mercer Room Concept

Mercer's office during the Necromorph outbreak.

"I can only hope one of his beloved Necromorphs finds him before I do."
Isaac Clarke in his personal log.

Even before the Necromorph infection began, Mercer was already showing signs of insanity, making fellow doctor Terrence Kyne distrust him. Before succumbing to dementia himself, Mercer ironically was one of the medical officers to study the colonists suffering from it, like Brant Harris. He even advised Kyne to bring more subjects to the ship in order to find out what was happening.[2]

When the Necromorph outbreak hit the colony, Mercer saw first the Hive Mind and the Necromorph transformation through recordings. He was convinced that they were the divine beings supposedly prophesied by Michael Altman.[3][4] Mercer even was the one who named the massive creature "The Hive Mind", making it one of the few named Necromorphs in-game.

When the infection reached the ship, Mercer's office in the Medical Deck became a laboratory for his experiments with the Necromorphs. His room was covered with Marker symbols, a drawing of the Marker on the floor and several messages including, "Make us whole!", "Save the Marker!" and "To join is to survive". He performed several medical experiments on the crew of the USG Ishimura, one of which resulted in the Hunter. Mercer's experiments were aimed at transmitting the infection to live subjects, which caused the Hunter's unique regenerative properties.[5][6] Mercer also attacked and killed numerous crew members and patients as the ship fell into chaos, as evidenced by the decapitated heads also found in his room. After performing his experiments, Mercer devised a plan to take some frozen Necromorph specimens back to Earth, despite the heavily deteriorated condition of the ship by then.

Mercer is finally encountered in Chapter 5, trying to hinder Isaac's efforts to kill the Leviathan by locking doors.[7][8] When Isaac reaches the Chemistry Lab in order to get the poison capsule, Mercer presents himself through a nearby window. He tries to convince Isaac that the Necromorphs are the salvation of mankind, the next step of evolution, and releases the Hunter to attack Isaac, locking him inside the lab. He is later seen when Isaac is ambushed by Necromorphs at the Intensive Care Room, trying to convince him to just give up and let them kill him. He leaves shortly before they enter the room, locking the door once again. When Isaac finds the required DNA sample, Mercer decompresses the entire Medical Deck and locks Kendra Daniels out of the controls, in another attempt to kill Isaac.[9] He is last seen at the Cryogenics Lab, telling Isaac his plan to make the infection reach Earth by bringing frozen Necromorphs there. He then leaves him to be killed by the Hunter, once more trapping him in the room with the creature.

While Isaac was busy killing the Leviathan, Mercer unfroze the Hunter.[note 1][10] After this, he is reencountered in Chapter 10, murdering the crew member Jacob Temple after having killed Elizabeth Cross. It is hinted through the scenery that Mercer went to the Crew Deck to murder any remaining infidel survivors and to advocate the mass suicide among his fellow Unitologists. He may have been there since he unfroze the Hunter.


Mercer and infector

Mercer getting mauled by an Infector.

"Your time has come. No need to be frightened. No reason to fight. Many have gone before us, and now it's time for us to take the voyage together, to transcend death... and let the future take its course. Join me, as I gaze upon the face of God!"
—Dr. Challus Mercer's last words.[11]

After Isaac defeated the Hunter, Mercer allowed himself to be killed by an Infector, becoming a Necromorph himself, an Enhanced Slasher[12]. When Isaac encounters him, Mercer is missing his head, presumably to reflect his "blind faith." Isaac Clarke made short work of the changed Mercer and euthanized him.[note 2]


Before his descent into madness, Mercer was a loyal and hardworking crew member aboard the USG Ishimura despite being a devout member of the Church of Unitology. After the Necromorph outbreak, Mercer became insane and attempted to aid the Necromorphs in their assault on the ship, believing that they were sent by God to destroy humanity. He sided with Captain Mathius in the belief that the Red Marker was a holy artifact but could tell that Dr. Kyne wanted the Marker away from the Ishimura. In an abandoned log tape, Mercer revealed that, while Dr. Kyne was studying the Marker to find a means of ending the infection, Mercer himself was experimenting on live crew members to create stronger Necromorphs.

It is interesting to note that, although Mercer was insane, he was still able to point out those who were under the influence of the Marker, as he did when detailing how Dr. Kyne mentioned speaking to his wife—noting that "Amelia Kyne has been dead for some years". It is uncertain how much Mercer was acting due his dementia and due to his pre-established fanatism. Mercer showed no interest or sympathy in the survival of the Ishimura's crew. He praised Isaac Clarke for surviving snare after snare, but believed that all attempts to survive on Clarke's part were pointless. Mercer also had very little humanity as he performed trepanation on a conscious colonist in order to directly infect them while they lived. He also bored holes into the skulls of other dead crew members to ensure easy infection.


  • Iranian-American actor Navid Negahban provides the voice and likeness of Challus Mercer in the original Dead Space. In the 2023 remake, Mercer is portrayed by Pakistani-American actor Faran Tahir.[13]
  • Notably, Mercer was not featured in any of the prequels for the first Dead Space, even though he is one of the main characters like Nicole Brennan, Terrence Kyne and Benjamin Mathius.
  • It's worth noting that both Faran Tahir and Navid Negabhan are good friends in real life.[14]
  • When the player first enters Mercer's office, a short, strident segue of music is played to denote the event. Another strident segue of music is heard if the player kills Mercer following infection.
  • A book entitled "Field Medicine" with the logo of the Earth Defense Force can be found in Mercer's office.
  • If the player acts fast enough, the Infector Mercer submits himself to can be killed before fully infecting him, both preventing the need to fight him as an Infector and ultimately robbing him of his final wish, though this has no impact on the game's story one way or another.
    • Strangely, in the last video log, it is seen that Mercer is perfectly fine when he gets killed by an Infector. However, as Isaac approaches the Infector and Mercer, the Necromorph is just getting ready to infect the corpse. He should've already been transformed by the time Isaac gets there.
    • If the Infector is killed before it can convert him into a Necromorph, Mercer's body is totally mutilated, bloody with bone and muscles visible as well as his head missing, even though in the earlier log it was clearly seen that Mercer was totally fine. The model is in fact merely a generic Ishimura crew model.
    • Like Captain Mathius, the resulting enhanced Slasher from Mercer's body is in no way special from the others encountered in the game.



  1. During Chapter 7, the Hunter can be heard and briefly seen. When the player is first going between Floor B and Floor D, while Floor C is still locked, the player can watch the locked Floor C go by and vaguely see the shadow of the revived Hunter snarling to itself and sharpening its claws. The claw sharpening is a signature movement of the Hunter; no other Necromorph does this.
  2. If the player is fast enough, the Infector can be killed before the transformation can be completed.