Fallout factions

==Mechanics==
There are no distinct faction mechanics in the game, with the attitude of most factions towards the player depending on scripts and quest progress, unlike reputation. Typically, aggroing one member of a faction will cause other members to attack on sight, unless the target is killed stealthily.
==Factions==
* Brotherhood of Steel (Lost Hills): The Brotherhood is well-known throughout the wasteland, but is also reclusive and secretive. The player has the opportunity to join the Brotherhood, which is the only way to obtain power armor and a slew of upgrades to main statistics, on top of other benefits.
* Caravan merchant (The Hub): The three largest caravan houses that dominate wasteland commerce are the Crimson Caravan, Far Go Traders, and Water Merchants. Together they control the Hub through the Hub's central council and the Hub police. 
* Children of the Cathedral (The Hub, The Cathedral): A seemingly benevolent religious faction, the Children are a front for the Unity, offering low-cost healing services. They are directly related to the main quest and a number of other quests, such as for Decker in the Hub.
* Followers of the Apocalypse (Boneyard Library): A peaceful group of scholars and healers operating out of the Los Angeles library, or what used to be it. They are investigating the Children, suspecting that their peaceful propaganda hides ulterior motives.
* Raiders - Khans (Khan Base): A violent, Mongolian-inspired group of bandits led by Garl Death-Hand, threatening Shady Sands.
* Underground (The Hub): The largest criminal organization in New California, led by Decker, seeking to establish control of the commercial interests in the wasteland. Friendly Lending Company is a front for loan sharking operations, operating entirely legally.
* Unity (The Cathedral and Mariposa Military Base): The army, society, and political structure organized by the Master to bring about the next stage in human evolution. The Unity is the late-game antagonist and super mutants belonging to it are encountered in fixed locations as well as random encounters. Nightkin are a subtype and subfaction within the Unity, distinguished by their superior mutations.
===Minor factions===
* Blades (Boneyard)
* Desert Rangers (New Vegas)
* Gun Runners (Boneyard)
* Friendly Lending Company
* Skulz (Junktown)
* Regulators (Adytum)
* Circle of Thieves (The Hub)
* Underground ghouls (Necropolis)
* Vault 13 rebels (Vault 13)
===Mentioned-only factions===
* Rippers
* Union of Atomic Workers
* Vipers
===Demo factions===
* Crypts and Fools are two factions unique to the demo, vying for control over Scrapheap.
==Religions==
* Children of the Cathedral: The belief in the Holy Flame and Cathedral doctrine. Centered in The Cathedral, with branches and Children faithful found in Necropolis, The Hub, Mariposa Military Base, and even Junktown.
* Dharma: The beliefs of the people of Shady Sands, rooted in Hindu traditions.
* Christianity
 
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