Metal Gear Sahelanthropus

The Metal Gear ST-84 was a nuclear-armed bipedal tank developed in the 1980s. Soviet in origin, 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
In 1984, XOF housed the ST-84 inside of a hangar that was presumably owned by them. Some time later, Eli stole and took command of the Metal Gear to chase down Big Boss, 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. Diamond Dogs had somehow managed to retrieve the Metal Gear and place it at Mother Base.

Behind the scenes
The Metal Gear ST-84 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.

It's possible that the ST-84 is actually the Metal Gear concept that Aleksandr Leonovitch Granin showed to Naked Snake, and later ended up in the hands of Huey.

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 apparently letting her suffocate.

In the launch trailer for Metal Gear Solid V: 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.

Appearances

 * Metal Gear Solid V: The Phantom Pain