The Commonwealth of the Stations of the Ring Line, also called the Hanseatic League, Hansa, Hanza, or Hanse, is a neutral trading station led by Rusakov / Loginov with allies in nearly every faction (except for Bandits). They are the main trading source within the Metro station, based on the Ring Line.
Polis is a mostly neutral station with ties to the Order, and is based below the Moscow State Library. It is led by the Polis Council.
The Rangers of the Order are a paramilitary organization based in Sparta, Polis, and the D6 bunker. They are a group of the most lethal soldiers in Moscow, and are led by a man named Miller. They often show up within the wasteland, and seem to guard Polis.
The Red Line is a large group favoring the Soviet Russia era, and is based in the Red Line. They are led by a man named Maxim Moskvin, and have no real allies.
The 1905 Confederation is an (Assumed) ideological confederation in control of Barrikadnaya, Uliza 1905 Goda, and Begovaya stations. Due to its position near Hansa, it is considered a satellite station.
The Arbat Confederation is a neutral station composed of Kieveskaya and it's surrounding stations. It is based in the Kieveskaya-radial, and has an unkown leader.
The Baumansky Alliance is a very vague, unknown station which focuses on the remaking of pre-war technology. They are an alliance between the three stations on the Arbatsko-Pokrovskaya Line: Baumanskaya, Elektrozavodskaya and Semyonovskaya. They seem to mainly supply Hansa with weapons and energy, as there is the Elektrozavodskaya factory powering the entire Metro station.
The Belorusskaya Trade Outpost is a group of stations consisting of Sokol, Aeroport, Dinamo and Belorusskaya. They are a neutral faction, which is the main supply for livestock within the Metro.
The Children of the Underground was a paramilitary group based in Hole Station, led by Maxim Kamarov. The tunnels to their home were collapsed when a seemingly endless wave of mutants attacked, and the remnants are now nowhere to be found.
The Savage Cannibals of the Great Worm Cult is based at Park Pebody and at both mouths of D6, and is mostly hostile. They are a technophobic, xenophobic, primitive society.
The Revolutionaries are a branching military group of the Red Line who harrasses the Fascists, and are based in Avtozavodskaya.
The Satanists are an incredibly vague group who believe the Metro to be the entrance to Hell. Their base isn't even truly known, though it is widely believed for them to be based in Pechatniki.
The Watchtower is a group which comprises many Jehovah's Witnesses operating and preaching out of a subway train turned monastery who believe that the end-times are already upon them and that the survivors of the great war are those selected by god to ascend to heaven.
The VDNKh Commonwealth is a fairly neutral series of stations based in VDNKh, Alexeyevskaya, and Rizhskaya of the Kaluzhsko-Rizhskaya Line. They have three seperate administrations.
The Bandits, as the name states, is a rag-tag group of criminals, cutthroats, and murderers from within the Metro, with no known leaders. There is a more organized version stationed in Venice, called "Gangsters", who are more like husslers and thieves.
Central Metro Command was a short-lived attempt by the high-up, politically and militarily important people of Moscow to keep the inhabitants of the Metro living like they had before the Great War.
The Dark Ones are sentient, humanoid, seemingly telepathic/psychokinetic creatures dwelling on the surface after the Great War. They are considered the main threat to those in the Metro, but are largely unkown as a whole.
The Mutants reffers to any and all mutants in and above the Metro stations. The animal ones consist of Dark Ones, Nosalis, Lurkers, Watchers, Demons, Spiderbugs, Shrimps, Librarians, Giant Amoeba, Biomass, Nosalis Rhino, Bear, Slime-slug, and Mutant Crows. The plant mutants are Liana, Radioactive Luminescent Mushrooms, and Spore Buds. The Supernatural Phenomenon, technically considered mutants, are Ghosts (Either as Darkness or Damned Souls), Anomalies, the Great Door, and the River of Fate.
Some fish, dogs, crows, cows, pigs, and other animals are still either slightly or not at all mutated, and can be found throughout the Metro.
The Polis Kshatriya is the closest Polis has to a military, led by Melnik and Kuzmich. The Kshatriya security branch is made up of mostly Rangers.
Stalkers are, technically, anyone who travels to the surface in search of items, whether it be to trade, keep, or hide. They are mainly allied with Hansa and Polis, both being the largest trading centers in the Metro.