The Underground is a mysterious faction consisting of sewer-dwellers who live underneath Washington, D.C. Nothing is known of their history or their intentions, although they appear to be scavengers who come up to the surface to gather supplies. They are hostile to anybody they encounter. Unusually, Underground enemies have no voice lines whatsoever, and are only audible through their heavy footsteps.
Encounters with the Underground are infrequent and mostly randomized, although they are most commonly found in D.C.'s sewer system, and also come out on the streets at nighttime. They make a scripted appearance in the side missions Beekeeper Jeff, Navy Hill Transmission, and in the beginning of the main mission Federal Emergency Bunker.
Visually, the Underground are identifiable by their all-black clothing, chains worn around their heads, pipes and tubes on their backs and the bright yellow flashlights. The Underground Tank wears heavy armor made from large chains and cinder blocks.
Underground units are armed with basic weaponry limited to semi-automatic rifles, shotguns, and knives. Their Throwers use special grenades that apply chemical damage to their victims. Their Tanks are armed with chainsaws and have an attack strategy that is similar to the Outcast Tank.
“ They mostly come out night... mostly. No, but seriously, they really do mostly come out at night. Hide your kidneys. ”
Basic infantry unit armed with semi-automatic rifles. Elite Variants have Concussion Mines.
“ Analysis of the toxic gas these guys use has mostly inconclusive, but whatever it is, I don't really our masks are up to the challenge of filtering it out. Maybe don't get caught up in it? ”
Special units armed with chemical grenades that apply effect damage to their targets. They are armed with pump-action shotguns.
“ We've had a real problem with some of these guys just popping around corners and knifing some of our residents. Really vicious, unprovoked actions. I don't really condone killing people, but I won't shed any tears for them. ”
Agile units armed with knives. They can throw their knives from a distance or rush their target with melee attacks.
“ Medieval motherfuckers. See, this is why our decision to live above the ground floor was such a good idea. Nobody wants to be beaten with a flail. ”
Armored unit equipped with rudimentary armor and a chainsaw. Tanks have no ranged weapons and can only use melee attacks; their chainsaws can apply the bleeding effect to their targets.