Parasite Unit

The Skulls were a military group that Venom Snake encountered in Afghanistan.

Behind the scenes
The Skulls are enemies that will appear in Metal Gear Solid V: The Phantom Pain. They were first introduced in the E3 2013 Red Band and Green Band trailers for the game, appearing alongside the Volgin-like fiery apparition as well as the Psycho Mantis-like child under the tagline of "Those who do not Exist." They are seen in a desert jumping in the air, then landing on the ground running toward the camera. They appear to be numbered, as the centermost soldier has "02" on his forehead.

Not much mention of them was made until May 2015 when gaming journalists were given a chance to play the game for a short time. These enemies were noted as being "commanded by someone familiar." Some have theorized that Skull Face may be the commander of these soldiers. In addition, fans have wondered if Psycho Mantis is the commander of the Skulls given their appearance is alongside a gas mask wearing child in the aforementioned trailer.

The Skulls are very powerful, and are bio-mechanical in nature. They are shown in the trailer to be extremely agile. Though they do not speak, according to Peter Brown. Their physical appearance has some similarities to Sundowner from Metal Gear Rising: Revengeance and even possess a similar form to that of Fatman from Metal Gear Solid 2: Sons of Liberty.