What is S. T. A. L. K. E. R.?

S. T. A. L. K. E. R. is a video game series developed by GSC Game World.

The games takes place in the Chornobyl Exclusion Zone(Zone).

In our world, in 1986, there was a disaster at the Chornobyl Nuclear Power Plant(CNPP).

In the S. T. A. L. K. E. R. universe however, there was another explosion in 2006.

Because of the second disaster, in the Zone died the military that was staying there.

It became obvious that the Zone should be quarantined, since people from the excursions didn't return.

Those who did return, reported that they saw some kind of creatures,

looking like mutated animals, humans and unidentifiable creatures.

There were also reported to be anomalies: unexplainable matter that defines laws of physics.

In those anomalies were also found artifacts: mutated objects(organic matter, minerals etc.). They cost a lot of money.

What are S. T. A. L. K. E. R. factions?

As a result of discovery of artifacts, a lot of people came in the zone, with their own idealities and goals.

Eventually the different people that came to the zone, started forming groups, also called factions.

There are a total of 15 factions: 10 uncut from the original trilogy, 2 cut

and at least 3 more in the upcoming S. T. A. L. K. E. R. 2.

This table(sort of) shortly explains all of the uncut factions in the original trilogy.

Loners / Free Stalkers / Stalkers
Loners are normal people that came to the Zone because they like the Zone,
or just want to earn more money by finding artifacts and completing risky jobs.
They are in a constant war with Bandits.
Their allies are: Ecologists, Clear Sky, Duty, Freedom,
Military
The Military is the ukrainian Military.
They consist of 3 branches: standard Military(poorly equipt, trained),
Spetznas(nicely equipt, poorly trained for the zone),
Military Stalkers(nicely equipt, Stalkers that signed a contract with the military,
and underwent special training). Their allies are Ecologists and Duty.
Monolith
Monolith are stalkers that went to the CNPP after the second disaster.
After those stalkers went back, they were very agressive and didn't talk with others.
They are the most responsible and biggest faction in the zone,
since they guard Pripyat, CNPP and other keypoints in the Zone from other people.
They have no known allies.
Duty
Duty is formed by ex-military soldiers that raided the CNPP in the 2007 military operation.
Duty aims to defeat the zone, since it has ruined their lives.
They are a complete counterpart to Freedom, because of this they fight very often.
Their allies are: Loners, Ecologists, Clear Sky, Military.
Freedom
Freedom is a clan of stalkers who fight for free access to the Zone,
and their views are somewhat anarchistic.
They are a complete counterpart to Duty, because of this they fight very often.
Their allies are: Loners, Ecologists, Clear Sky, Mercenaries.
Mercenaries
The Mercenaries are a private military force operating within the Zone.
They are professional soldiers who will do just about anything in the Zone,
ranging from retrieval, assassinations, body-guarding, etc.
Their allies are: Ecologists, Clear Sky, Bandits, Freedom.
Bandits
The Bandits are raiders and marauders of the Zone, usually poorly equipt,
ranging from petty thugs and gangsters to organized crime syndicates.
They are a complete counterpart to Loners, because of this they fight very often.
Their allies are: Freedom, Renegades.
Ecologists
The Ecologists are Ukrainian scientists sent into the Zone on behalf of the government,
but seem to be affiliated with outside organizations (namely, foreign governments)
Their main purpose is the study of all aspects of the Zone,
using scientific methods to further explain what the Zone is, and its purpose.
Their allies are every faction in the zone, with the exception of Bandits, Renegades and Monolith.
Clear Sky
Clear Sky are just like ecologists, but a lot less nerdy.
They are the most secretive faction in the zone.
They are not very powerful against other factions, but with their big knowlege about the zone,
creatures have no chance to withstand them. They are in a constant war with Renegades.
Their allies are every faction in the zone, except: Military, Bandits, Rengades, Monolith.
Renegades
The Renegades are just like bandits, but a lot more miserable.
They are the smallest and the most poorly equipt faction in the zone.
They are the main enemy of clear sky
Their only ally are Bandits, but also they cannot sometimes withstand them,