A.R.C. Soldiers are trained millitary personnel within Underhell. They were first encountered as enemies in the Parking Garage near the Mall, right after the player encounters the Gatling Turret. The soldiers had entered the Parking Garage using Three Humvees and advanced all the way through the complex.
During the encounter, the player would notice that the soldiers had parked their humvees at three seperate levels and splitting up their squad of 12 into fireteams of 4.
Their objectives and purpose for showing up at the Parking Garage is currently unknown. However the gas chamber scene hints that they were going to the U.D.R.C. Complex to eliminate targets using Gas that were quote "on the list" using the makeshift gas chamber.
Their arsenal consist of the following: Heckler & Koch MP5K, M3 Shotgun, M4A1, MP5 EOD, MP7, Riot Shields, Ballistic Shields, Gas Masks, and Riot Helmets.