It's more or less the Loathing guys' spoof of Lovecraftian style horror.Roberto (as far as we know, because it's never openly explained in the game, which is also on par with Lovecraft's style) is some eldritch being from the darkness of space, that was contained by the Vibrato civilization. Roberto's containment was weakening after so many long years without any upkeep, and with some of the Vibrato facilities losing power or getting destroyed from the passage of time. His power was able to slip out into the West, which is why the Cult spends all their time worshiping him, and trying to set him free.The spirals and markings you see on some of the mines and caves around the West are places where the veil of reality has grown especially thin thanks to his power leaking out, and Roberto's utterly alien presence is enough to drive mortal men mad from the revelation (if you look at or get near too many of the symbols in some of the mines, you can' even advance the quest, your character just says 'You want to get out of here RIGHT NOW'). The Vibrato questline is you barely learning enough to manage to recontain Roberto, and stop his eldritch presence from exerting its influence on the West.

The other three major sidequests (the Hellcows, the Clowns, and the El Vibrato areas) seem to be leading to fights against powerful enemies, but you never. Other West of Loathing Guides: How to Win Fort Memoriam Battles. Unlocked after learning 69 words of the El Vibrato language.

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