Alternative title: "Making Friends in the Zone"

G.A.M.M.A.'s progression system partly runs on your stalker's reputation: a measure of how well known they are in the Zone. There are two kinds of reputation, general and faction-specific. As your reputation increases, expect to face more challenging foes and more dangerous quests, but also be rewarded with better loot, better items at traders, and better rewards.

Reputation

Reputation can be steadily gained by winning firefights, killing higher-ranking stalkers, and completing quests regardless of faction. Completing main storyline quests tends to reward more reputation than radiant quests picked up from random stalkers.

In addition to your reputation, G.A.M.M.A. tracks the reputation of other stalkers. Higher-ranking stalkers are more likely to drop better guns, carry rarer items and artifacts and have better gear. This also means they are generally harder to kill.

Factions

There are 12 total factions in G.A.M.M.A. - ten from the base game, and two new factions added by Anomaly. In this game, "IFF" is provided by your ability to recognize faction patches as they show up on your HUD. Therefore it is worth learning which patches correspond to which faction.

Loners	Clear Sky	Ecologists	Duty	Freedom	Mercs	Monolith	Renegades	Military	Bandits

There are two more factions added by Anomaly: Sin and UNISG. In the interests of spoilers, I will not describe them here, only to say that they are relatively late-game factions.

Players' starting reputation with these factions depends on their choice of starting faction. Players can also check the Relations tab of the PDA in order to see their current reputation with different factions, as well as factions' relationships with each other.