The Parasite Unit, also known as the Skulls, were an elite unit of parasite-enhanced super soldiers commanded by XOF commander Skull Face. Considered to be his most fearsome assets, the Parasite Unit were given high-priority missions that the average XOF soldier couldn't handle, given their supernatural abilities, especially their inhuman resilience. Venom Snake first encountered them in Afghanistan and later in Central Africa.
Sometime before the early 1980s, Skull Face discovered an old Diné man under the moniker Code Talker who had discovered a species of parasite from the remains of The End. Certain strains of the parasite would bestow upon the host mysterious abilities if the body accepted the parasite. Skull Face implemented the parasites alongside additional technology to numerous XOF operatives in order to create the "Parasite Unit", also known as the "Skulls."
Their earliest known activities involved the capture of Kazuhira Miller in early 1984, whom they spared after killing his entire unit and decidedly gave him to the Soviets. Miller implied that Skulls may have spared him and handed him over to the Soviets by accident. Later, after Venom Snake rescued Miller from Da Wialo Kallai, the Mist Unit of the Skulls attempted to kill Miller along with Snake, but ultimately failed as Snake and Miller made their escape via helicopter. They later reappeared during Snake's mission to acquire the Honey Bee at Da Smasei Laman, where they were ordered by Skull Face to kill him, but again failed to do so.
The Skulls were later redeployed into central Africa to personally escort a convoy of armored vehicles, protecting a transport truck which carried nuclear weapon "yellowcake" and uranium enrichment archaea. When Venom Snake embarked on a mission to extract the truck and its contents, the Armor Unit revealed themselves after Snake moved into the truck's vicinity. Discovering Venom Snake's location, they attempted to kill him and prevent his stealing of the cargo, though Snake was able to extract the truck and fend them off. Later during Venom Snake's mission to extract Code Talker, the Camouflage Unit attempted to stop him from reaching Code Talker's residence in Lufwa Valley. Ultimately, Venom Snake met with Code Talker and the Camouflage Unit could not prevent Snake from extracting him out of the area. While Code Talker and Snake were en route to Mother Base via helicopter, the Armor Unit tried to prevent them from reaching their destination, taking down Snake's helicopter using a cloud of corrosive metallic archaea. After succeeding in grounding the helicopter at the Nova Braga Airport, the Skulls moved in to execute the crash survivors, but Venom Snake managed to fend them off and escape with Code Talker.
After Skull Face's death, Code Talker assisted in the creation of the Parasite Suit for the Diamond Dogs, a special combat suit that would allow the user access to some of the supernatural abilities of the Skulls using parasites extracted from their bodies. Diamond Dogs were eventually able to extract and capture a few of the Skulls while operating in the AO. Upon capture, Diamonds proceeded to depower them by extracting the parasites within their bodies, though this did not revert the physical mutations their bodies had undergone when they were infected. Unable to revert the captured Skulls back to their original forms, they are held prisoner aboard the Quarantine Platform on Motherbase.
In addition, the Parasite Unit itself eventually resurfaced and proceeded to attack one of the FOBs of an allied Private Force of the Diamond Dogs, No Alert, with their being forced to ask for Diamond Dogs' help in driving out the Parasite Unit for good. The Parasite Unit in this case had been sent to No Alert's FOB by a rival as revenge.
Personality and traits
The Parasite Unit wore technologically advanced suits that could be used as camouflage to appear as a member of a different organization. They received their powers from a species of parasite discovered by Code Talker. It destroyed most of their cognitive functions, leaving them to effectively become zombies both physically and mentally. Despite this, however, they did have a limited capacity for speech. This was demonstrated by their first encounter with Venom Snake in Afghanistan, where they were heard yelling "Snake" in a rasped tone. Miller also implied that they may have spared him and handed him over to the 40th Army by accident. The parasites that granted them their abilities primarily resided over their skin, maximizing their physical capabilities, including having them easily catching up with a moving vehicle and/or horse just by sprinting, moving at such a speed that it appeared as if they were teleporting, being capable of sustaining significant damage as well as surviving a high landing without injury, and having powerful enough leaps to disappear into the sky when retreating. Members of the Parasite Unit normally operated in groups of four, and three variant types existed based on their capabilities and specialties. Their combat prowess and lethality was such that even ordinarily highly-secure places could afford to maintain relatively little actual manpower in the area simply due to the Skulls' presence, as implied by Ocelot in Lufwa Valley, where he noted the facility, despite their level of security, had the path seemingly being deserted instead of having at least one patrol operating. In addition, the eyes of the Parasite Unit were shown at times to shine green in dimly-lit areas, implying that they were able to see in the dark.
The Mist and Armor units were infused with metallic archaea, allowing them to use it to give them other abilities. The Armor Unit's armoring ability; their metallic, boulder like projectiles; their ability to create metallic spike structure erupt from the ground as a shielding like wall against attacks; and the spikes being able to crash vehicles and harm nearby enemies all originate from metallic archaea. The Mist Unit's ability to create corrosive gas and clouds that turned any metal instantly to rust were also caused by metallic archaea in its corrosive form. It was also heavily implied that they could form their weapons such as machetes and sniper rifles from metallic archaea. The presence of metallic archaea in these skulls were the blue or orange sparkling in the black gas they generate, as well as their blood also being seen as glowing blue. Both the Armor and Mist Units were also capable of infecting any soldiers in close proximity at will with metallic archaea, turning them into "puppet soldiers" to ensure efficiency. At the very least Zero Risk Security had been aware of this, as the truck driver delivering their cargo had been given strict orders to never open the canvas of his truck, nor to let anyone inspect the truck under any circumstances, and it was rumored that doing so would result in possession by the Kikongo god "Nzambi."
Despite their combative prowess, however, they possessed a number of weaknesses. The parasites on their skin were drawn to freshwater, and contact with heavy amounts of it would force the Skulls to absorb them, leaving them in a vulnerable state. They also had difficulties distinguishing between Snake and a balloon decoy, to the point where they would attack both Snake and the decoy interchangeably. In addition, while infused with metallic archaea and capable of using it in various ways, Camo unit nonwithstanding, they weren't invulnerable to being harmed by anything coated with it, including their own weaponry. This was best demonstrated if Venom Snake parried one of their blows, where he would proceed to stab them with their own machete, which was capable of penetrating even an Armor unit's armored state.
The Camouflage Unit 
Unlike the other two Skull variants, the Camouflage Unit, also called the Camo Unit, was an all-female variant of the usual four, in which they possessed an augmented scope equipment covering their right eye, the eyepiece being remarkably similar to the Solid Eye. They were able to cloak their bodies to the point of being nearly invisible to the naked eye, serving as their camouflage during sniper combat or whenever they attacked up-close, which was achieved via their parasite variant altering their skin's pigment.
They acted almost identically to Quiet, possessing laser-sight sniper rifles stored inside their parasitic skins. They also possessed many of the same abilities as the Mist Unit, including their misty presence and enhanced agility and speed. However, they were somewhat frail in comparison to their male counterparts, capable of withstanding only three or four headshots from a sniper rifle. They also used machetes with corrosive archeon edges when engaging their enemies in close combat, employing the use of their stealth camouflage to sneak up on them.
This version of the Skulls possessed no metallic archaea, giving them no special abilities other than those given by their parasite enhancements.
The Mist Unit
The Mist Unit were generally assigned to handle retrieval missions, often ambushing their targets when they least expect it. This variant of the Skulls had bright, glowing eyes. True to their namesake, their presence was marked by a thick cloud of cyan mist setting down on the area around them, using it as a form of cover to both hide their numbers and to confuse their enemies. When unprovoked they normally lumbered around like zombies, but in actuality, they were extremely agile, possessing the ability to jump at heights and distances that made it appear as though they were flying or gliding for a short time. They were able to outrun D-Horse and most vehicles, leaping and bounding at incredible speeds to catch up and assemble into formations ahead of their targets.
They had the ability to store weapons and would often use the G44K bullpup assault rifle and machetes with corrosive edges of metallic archaea that can pierce through armored vehicles. They could also release clouds of metallic archaea underneath their parasite skin, releasing them at will in order to infect other soldiers and controlling them to attack on their behalf, similar to how The Pain controlled his hornets. They were also able to form huge structures of metallic archaea as a way of shielding themselves from enemy fire. Likewise, it was also used as a means of attack, as it could be shot from the body as a projectile, made into levitating boulder-like shapes that flung themselves towards an enemy, or infused into the ground to cause sharp, spike-like structures to burst from it as a means of attack.
The Armor Unit
This unit of the Skulls behaved and attacked similarly to the Mist Unit, using G44K bullpup assault rifles and machetes with corrosive archeon edges, though they were much taller and bulkier in appearance. Their specialty was their ability to generate archaea all over their bodies which acted as armor thus greatly enhancing their durability. They could release clouds of metallic archaea, turning them into a form of corrosive dust as means of dissolving or disabling their targets, be it humans or armored vehicles.
Similar to their ability to create hardened armor, they were able to channel hardened archaea through the earth, summoning them out of the ground as means of attacking their target. The explosive properties of the archeon material also acted as a form of explosive and served to deal critical damage on their targets. Their telekinetic control over the material allowed them to form hardened archeon structures in spike or boulder-like shapes. They could infuse it into the ground to make spike-shaped structures erupt from it as a means of attack or to shield themselves, as well as form levitating structures that flung themselves at a target. With the latter ability, two Armored Units also were prompted to retreat immediately before the structures were flung, presumably to ensure they didn't get caught in the crossfire. Much like the other units, they were capable of producing mist, albeit to a much lesser degree than the Mist and Camouflage Unit. Much like the Mist Unit, they moved at top speeds when traveling and could release clouds of metallic archaea to infect any soldiers within their vicinity and act as their support during combat.
Behind the scenes
The Parasite Unit are enemies that appear in Metal Gear Solid V: The Phantom Pain, serving as some of the notable bosses within the game, like many of the other special forces units in the series. They were first introduced in the E3 2013 Red Band and Green Band trailers for the game, alongside the Man on Fire and Tretij Rebenok under the tagline of "Those who do not Exist." They were seen in a desert jumping in the air, then landing on the ground running toward the camera. However, this footage isn't featured in the final version of the game and certain design elements of the Skulls were also changed, i.e. the finalized version of the Mist Unit having glowing eyes.
No mention of them was made until May 2015 when gaming journalists were given a chance to play the game for a short time. They were originally noted as being "commanded by someone familiar." It would later be confirmed that Skull Face was the commander of the unit.
In the Piggyback Collector's Edition Guide's Art Gallery, Hideo Kojima explained that the Skull Unit is a new arrangement of the respective models of real special forces, American comic style, mysterious individuals, beasts, and huge AI weapons for Metal Gear Solid, Metal Gear Solid 2: Sons of Liberty, Metal Gear Solid 3: Snake Eater, Metal Gear Solid 4: Guns of the Patriots, and Metal Gear Solid: Peace Walker. He also added that unlike before, they aren't merely a single boss but boss enemies that work as a team.
Though Venom Snake is able to incapacitate the Parasite Unit during his battles with them, it is impossible to kill them. After they are neutralized, provided the player doesn't Fulton them beforehand, they will simply stand up while regenerating their bodies and vanish. After Skull Face is killed, their fates are left unknown.
The Wandering Mother Base Soldiers that are the subject of several side ops share a similar character animation to the Parasite Unit, including staggering as they walk. In their case, however, it is heavily implied that their actions are the result of their becoming erratic from wandering various battlefields for a prolonged time as well as the isolation from doing so.
In The Art of Metal Gear Solid V booklet, in addition to the Camo, Mist, and Armored Skulls, there was a fourth type of Skull who looked as if he was screaming and had the number 17 branded onto his head. In addition, another concept art had a Camo Skull with what looked like an earpiece, which implied that the Skulls were originally going to have actual dialogue instead of simply making feral roars. Some concept art for the Skulls were later reused as photograph props within various outposts/guard posts.
The Skulls serve as miniboss encounters throughout the game. Skulls are encountered in Mission 1: "Phantom Limbs", Mission 6: "Where Do the Bees Sleep?", Mission 16: "Traitors' Caravan", Mission 28: "Code Talker" and Mission 29: "Metallic Archea". They can travel long distances and move with such speed to the point of outrunning D-Horse and most vehicles. When they are not alerted to the player's whereabouts, they walk in a slow, stumbling motion, akin to that of a traditional zombie.
The Mist Unit's boss segments operate with a misty environment that blur the surrounding area as well as lowering the visibility levels a few meters ahead of the player's line of sight, similar to the effects caused by a sandstorm within the game. They primarily use G44 assault rifles to attack, and for close range, they employee the use of glowing machete: they will combine this with their teleportation ability to suddenly appear in front of the player character and attack them with a single brutal strike, delivering enormous damage. They are able to summon large chunks of metallic archaea that act as a cover/shield from enemy fire, often summoning them in a row to form a barrier. During their first boss encounter, the player can either avoid alerting them, alert them and then flee until they exit the Hot Zone, or defeat them using lethal or non-lethal attacks. Leaving without alerting them is one of the mission goals, though it is very difficult to achieve on the first run through the mission as the Skulls do not respond to most normal methods of distraction.
If the player engages them in combat while Miller is left unattended, the Mist Unit will eventually home in on his location: if they reach him, they will instantly kill him. The player can also fight and defeat them on horseback while Miller is being carried on D-Horse. In the second encounter at the end of "Where do the Bees Sleep?" they are fought again, this time with the added ability to create puppet soldiers from a small group of enemies that spawn at the start of their boss encounter, plus any soldiers from the Smasei Fort garrison who were not Fultoned during Venom Snake's infiltration.
The Camouflage Unit was only fought once and they functioned similarly to Quiet's boss fight, albeit as a group of four snipers with similar attack functions as the Mist Unit. They still produce a misty environment though it only mainly serves to cover the skies and lower the visibility at a long range. They are able to camouflage themselves to the point of being invisible, akin to the function of the stealth camo (though this does not negate the iDroid's ability to mark them). If the player stays too long in one area without being spotted, they often try to move closer and stealthily ambush the player using their machetes.
If the player engages the Camouflage Unit upon meeting them and is spotted, guards at the mansion are put on alert which results in more enemy personnel and vehicles arriving at the area after meeting with Code Talker. Alternatively, if the player neutralizes the Camouflage Unit without being spotted by them at all, the guards at the mansion will not be on alert. If the player sneaks past the Camouflage Unit when they first appear, the boss fight will be nullified. In this instance, after making contact with Code Talker, the enemy personnel guarding the area will instead be replaced by infected soldiers. Additionally, this resulting circumstance grants the player a second chance to engage the Camouflage Unit in a boss fight, though it is also possible for the player to sneak past them again and avoid the boss fight entirely.
The Armor Unit's boss encounters functioned similarly to the Mist Unit but with additional abilities and functions. They possessed the highest durability by comparison due to them being able to produce archeon armor that gave them twice the amount of their life gauge; one for their bodies and one for their armor. They could easily regenerate this armor, even when their bodies' respective life gauge is greatly depleted; forcing the player to damage the armor before being allowed to permanently deplete their bodies' life gauge again. They could also channel hardened archaea through the ground as means of attacking the player, similar to Sahelanthropus, albeit at a much smaller scale.
When their armor's life gauge is completely depleted, they tend to move far away and attack at long range; preferring to use their automatic firearms as well as throwing hardened archaea at the player using telekinesis. Whenever their armor has regenerated they would profusely attack the player and often engage in close-ranged combat, switching between using their G44K bullpup assault rifles or continuously employing melee attacks with their machetes. They are known to protect one another by summoning hardened archaea between the player and their fellow unit members.
If the player enters a vehicle during the second encounter with the Armor Unit, they surround themselves in a dust of corrosive metallic archaea which will disable the vehicle should the player drive close to them. Though the Armor Unit is able to produce mist during this encounter, visibility levels remain the same and it only prevents the player from attempting extraction via helicopter. Similar to the Mist Unit, they were accompanied and assisted by puppet soldiers
The Skulls possessed a number of weaknesses that the player could exploit. The tendency for the Mist and Armor Units to teleport to close range at regular intervals could easily be exploited through the use of shotguns, and they were also susceptible to armor-piercing firearms and were exceptionally vulnerable to knockout gasses such as those from sleeping gas grenades. In addition, they lock onto both the presence of Snake and any balloon decoy that is deployed, causing them to attack the closest target due to being unable to distinguish between the decoys and Snake. Should the player change the weather conditions to rain, the Skulls will remain idle due to their insatiable desire to drink water. The Skulls are also unable to climb ladders, and so if the player can get on top of a tall building where they cannot be attacked from the ground (such as the hangar in "Metallic Archaea"), the attack options of Skull soldiers will be severely limited.
A counter prompt will appear during their melee attack if the player character is not occupied with some action that precludes it; if the relevant button is pressed in time, it will result in Venom Snake counter-attacking them with their own machete (which depending on the specific melee attack, will either have Snake's parry involve stabbing them in the gut, or knocking them to their knees and then jamming the blade through their neck). This move deals extremely high damage and also inflicts a prolonged stun state, allowing for additional damage.
It is only after building the Quarantine platform and completing Mission 29 that the player is finally able to extract the Skulls via fulton recovery when replaying any encounter with them. When extracted, they will be located on the Quarantine platform of Mother Base, with the Camouflage Unit sharing a cage, while the Mist and Armor share the other. They will only stammer around in their confinement and cannot be interacted with.
The player can also unlock the Parasite Suit for Venom Snake's use, which grants the player mist, stealth camo, and armor abilities derived from the Mist, Camouflage and Armor Unit respectively. Use of the Parasite Suit's various abilities is limited though, and if the player completely depletes the cartridge supply during missions, it will remove the respective Skulls from the player's Quarantine platform due to the cartridges being derived from their bodies. To prevent this, the player must stock up on the material by constantly extracting the Skulls through replays of their respective boss encounters.
The Skulls Attack
On the December 17 update, the FOB Event Mission called "The Skulls Attack" was planned to be distributed, though for reasons unstated, it was not released with the update. The event was released on December 29, involving a contract for Diamond Dogs to eliminate 3 squads of Armor Unit Skulls on an FOB.
The Parasite Suit that Venom Snake can develop.
- ^ 
- ^ Metal Gear Solid V: The Phantom Pain, Kojima Productions (2015)
Mission 28: Code Talker
Ocelot: No sign of the enemy. Judging by security in the area [Lufwa Valley], I'd expect to see a patrol by now...
- ^ Metal Gear Solid V: The Phantom Pain, Kojima Productions (2015).
Mission 16: Traitor's Caravan
Soldier: You ready to set off? // Truck driver: Anytime. // Soldier: What is it under the canvas, anyway? // Truck driver: You're better off not knowing. Besides, you'd violate our contract if you look. // Soldier: I've heard rumors... You think it's true that anyone who you looks under the canvas will be possessed by Nzambi? // Truck driver: Do not look under the canvas. // Soldier: Right. So you're driving to the Munene River? // Truck driver: Yeah. Do me a favor and contact the outpost there. // Soldier: You got it. // Truck driver: Watch my back out there, guys.
- ^ Metal Gear Solid V: The Phantom Pain, Kojima Productions (2015).
Mission 16: Traitor's Caravan
Truck driver: Something wrong? // Soldier: Need to inspect your cargo. // Truck driver: Hey, cut it out! You know the rules. Open that canvas and my client will go berserk. // Soldier: You think I give a shit? // Truck driver: We have an agreement. You'll be charged with a breach of contract! // Soldier: Tell your boss to send a bill. // Truck driver: What the hell, man? // Soldier: There's an infectious disease going around our post downstream. It's likely it was set loose by another PF. // Truck driver: And you're blaming us? // Soldier: I never said that. But right now we're all a little touchy about outsiders. Just one look and we can clear this up. // Truck driver: I ain't taking the fall for this...! // CP: (Via soldier's radio) This is CP. Let the convoy through. HQ has just contacted us. The message is: "We have a collaborative relationship with Zero Risk Security in this matter. Unilateral actions in the field will not be tolerated." "Unilateral actions in the field will not be tolerated." Those were HQ's orders. We have no choice.
- ^ https://www.youtube.com/watch?v=y-c1a5c55-8
- ^ https://www.youtube.com/watch?v=NL4ZxDWLwpM
- ^ https://www.youtube.com/watch?v=g3fWCNPo7sI
- ^ a b http://www.metalgearinformer.com/?p=19265
- ^ http://www.metalgearinformer.com/?p=20422
- ^ https://twitter.com/HEITAIs/status/928194711528947712