Parasite Unit

Mist = Camouflage = Armor = The Parasite Unit, also known as the Skulls, were 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 soldier couldn't handle, given their supernatural abilities, especially their inhuman resilience. Venom Snake first encountered them in Afghanistan and later in Central Africa.

Their prowess in combat was first hinted at when they wiped out Kazuhira Miller's unit in minutes before capturing him.

History
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 as a sign of good faith. This proved to be a ruse as the Skulls had actually spared Miller to lure out Big Boss. 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 the 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 closely near the truck's vicinity. Discovering Venom Snake's location, they attempted to kill and prevent him from stealing 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 onto 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. 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.

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). The parasites that granted them their abilities primarily resided over their skin, maximizing their physical capabilities. Members of the Parasite Unit normally operated in groups of four, in which three variant types had existed based on their capabilities and specialties.

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, and their ability to create metallic spike structure erupt from the ground as a shielding like wall against attacks, as well as 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. 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 the cargo had been given strict orders to never open the canvas of his truck nor to let anyone inspect the truck under any circumstances, as well as it being rumored that opening the canvas will result in everyone becoming "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 will 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 will attack both Snake and the decoy interchangeably.

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. Also unlike the other two variants, the Camo Unit, if defeated, did not retreat when the mist dissipates. 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 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. 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 metalic 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, as well as create and shoot spike like structures at their enemies and infusing the ground with it, causing spikes to burst from the ground, both of these being 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. They were also capable of throwing these hardened archeon structures through their telekinetic control over the material. 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 other special forces unit in the series. They were first introduced in the E3 2013 Red Band and Green Band trailers for the game, appearing alongside the Man on Fire as well as 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 is left unknown.

A Japanese development blog revealed that Skulls may potentially act as a defense at an FOB in a future update.

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.

Gameplay
The Skulls served as various bosses throughout the game. Each Skull encounter can be found 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" as boss enemies. They could travel long distances and moved with such speed to the point of out-running Diamond Horse and most vehicles. When they are not alerted to the player's whereabouts, they walked in a slow, stumbling motion, akin to that of a traditional zombie.

The Mist Unit's boss segments operated with a misty environment that blurred 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 used bullpup assault rifles to attack, and for close range, they employed the use of machetes in which they could could swiftly move near the player and attack them with one strike. They were able to summon large chunks of metallic archaea that acted 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 exit the Hot Zone or defeat them while carrying Miller.

If the player engages them in combat while Miller is left unattended, the Mist Unit will eventually home in on his location and immediately kill him. The player can also fight and defeat them on horseback while Miller is being carried on D-Horse. In their second boss fight, they were accompanied and assisted by infected soldiers.

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 defeats the Camouflage Unit upon meeting them, guards are put on alert which results in more enemy personnel and vehicles arriving at the area after meeting with Code Talker. 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 boss fight, the Armor Unit would surround themselves in a dust of corrosive metallic archaea which will disable the vehicle in use should the player drive close to them. Though the Armor Unit is able to produce mist during their boss 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 infected soldiers during their second boss fight.

The Skulls possessed a number of weaknesses that the player can exploit. They were 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.

In addition, if the player is able to counter their melee attacks in time, it will result in Venom Snake damaging them with their own machetes (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), in which it also stuns them long enough to create an opening to further damage them.

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 boss 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, in which it 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.