Metal Gear Sahelanthropus

The ST-84 Metal Gear, also known as Metal Gear Sahelanthropus, was a nuclear-armed bipedal tank developed in the 1980s. Soviet in origin but utilized by XOF, Huey Emmerich was suspected to have helped built it. In neutral position, it stood approximately 15 meters tall. The ST-84's capabilities and purpose were unknown at the time of its development.

History
Huey Emmerich was commissioned by XOF and Cipher to create the ST-84. However, the design of Sahelanthropus could not allow anyone other than a child to man the vehicle due to the small cockpit. This resulted in a falling out between Huey Emmerich and his wife, Strangelove, as he decided to use his toddler son Hal as a guinea pig to test the machine, something the latter vehemently disagreed with, which ultimately resulted in her death via suffocation by being trapped inside The Boss AI's casing by Huey.

Sahelanthropus is first seen in Mission 6: Where do the Bees Sleep? after Venom Snake has recovered the Honey Bee from the caves of Da Smasei Laman. While exfiltrating the cavern, a fog appears around Snake similar to the mist used by the Skulls. Snake sees Tretij Rebenok, and before he can react is suddenly grabbed by the ST-84's giant hand from within the mist. After a momentary black-out, Snake awakens upside-down and still in the grasp of the Metal Gear's fist. Skull Face appears and taunts him before the hand drops Snake onto the ground, opening its palm to act as a platform for Skull Face to stand on. Skull Face, Rebenok, and Sahelanthropus then depart into the fog, leaving Snake to battle against a platoon of Skulls.

The ST-84 is first seen in full by Venom Snake on his mission to make contact with Huey and extract him from Soviet-controlled Serak Power Plant in a Side Mission. Behind the power plant is a large cave that has been modeled into a makeshift hangar for the continuous construction of Sahelanthropus. Skull Face, having grown impatient, is seen arguing with Huey over Sahelanthropus' current status. Huey insists they wait until the AI is fully operational, but Skull Face claims that giving the Metal Gear weapons AI would be the same mistake Hot Coldman made, instead planning for Rebenok to pilot it using his psychic powers. Skull Face deduces Huey's plan to defect and has him moved to the Afghanistan Central Base Camp as the ST-84 retreats into the depths of the hangar, kicking off Mission 12: Hellbound. At the Central Base Camp Venom Snake finally manages to rescue Huey, but their exit is interrupted by Sahelanthropus, Skull Face, and Rebenok inexplicably landing out of the sky in front of them. Skull Face retreats to an XOF chopper and orders the ST-84 to attack the two. Snake and Huey manage to evade Sahelanthropus and board a Diamond Dogs chopper. When Sahelanthropus attempts to jump into the air and strike the chopper Venom Snake opens fire on it using the chopper's minigun and manages to destroy its left arm and leg, sending the Metal Gear crashing back into the ground.

During the final confrontation between Venom Snake and Skull Face's forces, Tretij Rebenok decidedly activated the ST-84 prematurely. Unbeknownst to either Venom Snake and Skull Face, Eli hijacked the Metal Gear by using Tretij Rebenok as a conduit; as means of enacting vengeance against Venom Snake. Its loading platform was also responsible for crushing Volgin's body. The Eli-controlled Metal Gear would chase down Venom Snake, but was stopped by a narrow gap in the canyon it was running in, forcing Eli to switch the Metal Gear into a more humanoid configuration and later causing further mayhem with what seems to be a plasma whip. Wreaking havoc upon the XOF soldiers, Sahelanthropus confronted and attacked Skull Face, resulting in him being trapped under debris. Eli would then focus his efforts on attempting to kill Venom Snake by using the Metal Gear. After a prolonged battle, Venom Snake was able to incapacitate the Metal Gear thus removing Eli's control over it. Diamond Dogs then retrieved the Metal Gear and placed it at Mother Base.

Eli later hijacked the Metal Gear at Mother Base, having allied himself with Tretij Rebenok. The fact that someone who had far more of a lust for revenge against Venom Snake than the Man on Fire left Skull Face so shocked that he couldn't even bring himself to evacuate, necessitating two of his soldiers to physically drag him out to safety. Sahelanthropus then did a huge number on the various military hardware that Skull Face dispatched to take it out with little effort, also proceeding to crush Skull Face by kicking a downed communications tower onto Skull Face, leaving him mortally wounded. Sahelanthropus was later stopped by Venom Snake, and then brought to Mother Base at Huey's request, although Huey secretly repaired Sahelanthropus, where it would be hijacked again by Tretij Rebenok and Eli. The two would take the rest of Eli's child soldiers via helicopter back to Africa along with the ST-84; establishing a new stronghold that is likened to the Lord of the Flies. In an effort to neutralize Eli and his forces, Snake and a detachment of Diamond Dogs traveled to the Island to put an end to Eli's chaos. Unknown to them however, the XOF discovered Eli's location in Africa and sent a small platoon of soldiers to kill him and retrieve the Metal Gear so it could be brought back under their control.

Behind the scenes
The ST-84 Metal Gear was first revealed in the E3 2014 trailer of Metal Gear Solid V: The Phantom Pain. More details of it were given in the E3 2015 trailer and the Japanese special edition of The Phantom Pain. ST-84 is short for Sahelanthropus Tchadensis 84. Its full name was written in the trophies list. The Sahelanthropus is an extinct hominine species possibly very close to the time of the chimpanzee-human divergent. This name is symbolic of Metal Gear being the missing link between infantry and artillery and this specific one's namesake being a likely candidate for the missing link between human and ape. While the ST-84 initially resembled Metal Gear REX, the final version features 2 hands, a rib cage, 2 missile launchers, and a head designed to resemble a Sahelanthropus skull.

A leaked page from an Italian game guide reveals that ST-84 can walk upright in a humanoid form. In addition, the same guide also revealed that ST-84's development was indirectly responsible for Strangelove's death, as she had accidentally locked herself inside the Mammal Pod after a falling out with her husband, Huey Emmerich, regarding whether they should or shouldn't use their young son Hal Emmerich as a test subject for ST-84, with Huey letting her suffocate. Additionally, the color scheme and the general shape of humanoid form of sahelanthropus bears a resemblance to the orbital frame Naked Jehuty from Zone of the Enders: the 2nd Runner (another Kojima game), albeit a more bulky form and less advanced version.

In the launch trailer for The Phantom Pain, ST-84 appears again chasing snake when it gets stuck between two rocks, then it reveals and uses it's two arms and achieves breaking through the hollow while Tretji Rebenok stands flying near him. Snake hides while the Metal Gear takes out it's plasma whip and starts attacking the base. The effects of its plasma whip result in rock fissures emerging, similar to a scene in the Gamescom 2014 trailer.

Its inspiration was explained by Hideo Kojima on a series of Twitter posts: Specifically, he decided to base ST-84 Metal Gear on the Sahelanthropus, citing that it was connected to the Pangaea concept from MSF as well as the theory that humans were able to among other things develop language upon becoming upright, with ST-84 paralleling this theory by him stating that for evolution to proceed forward to the new world, one needs to stand up. He also denied that it was an homage to the Tokusatsu anime that ST-84 Metal Gear was able to walk upright, though he did admit that Guillemaro del Toro liked the idea when he showed the cutscene to him in 2013 and noticed a Jason and the Argonauts homage in the scene. The Piggyback Collector's Edition Guide's Art Gallery annotations by Hideo Kojima reiterate these elements, and also elaborates that the vocal cord parasite theme goes hand in hand with the Sahelanthropus element.

The name "Sahelanthropus" and reason given for the name within the game represents something of an anachronism. The Phantom Pain takes place in the '80s. However, the first Sahelanthropus skull was not found until the early 2000s.

Appearances

 * Metal Gear Solid V: The Phantom Pain