Altruist Camp

The Altruist Camp is the main headquarters of the Altruist Cult, situated in the heart of the Chiliad Mountain State Wilderness in San Andreas. It is almost completely isolated from the rest of civilzation, giving it a creepy atmosphere. The camp itself is made up of many wooden shacks, abandoned houses and a water mill, and it's surrounded by large walls.

The Altruists living here are hostile to any outsiders, except for Trevor Philips. However, after Trevor manages to kidnap enough people to bring to the camp, the Altruists will betray Trevor. This is a bad choice, as Trevor overpowers the cultists and eventually kills all Altrists in the camp;

When Trevor does his gun dealing flights over Blaine County, one of the targets to drop out weapons is the cult camp. Oddly enough, the target still appears even if Trevor erradicated them in the Strangers and Freaks mission.

Events of GTA V
The Altruist Camp is not particularly featured in any storyline missions during Grand Theft Auto V, but certain characters involved in Strangers and Freaks can be kidnapped by Trevor to be taken to the camp. After he manages to capture four people, the cultists will suddenly turn hostile, and open fire on Trevor. He escapes, steals several weapons and cash, and burns down the camp. After the battle, the camp will be abandoned and in ruins.

Trivia

 * The Altruist Cult is one of two locations in GTA V where the player can encounter nudity. The other is the Vanilla Unicorn. However in the Vanilla Unicorn, you can only find partial nudity.
 * Within the facilities, the camp contains a Medi-kit, two Body Armors, an RPG, an Assault Shotgun and a Baseball Bat in the altar. All of them respawning in a very short amount of time.
 * The Altruist Camp can be accessed from the far left corner of the wall near to the cliff. This place is a good source to get the RPG and the Assault Shotgun earlier in the game and ammo spawns very quickly, allowing the player to save up. Even though it's populated with cultists that keep respawning, they're equipped only with Pistols, thus making easier to hoard ammo and be fairly safe as two body armors also keep respawning.r