LORE: The Reclamation War was a brutal conflict fought between the fractured powers within the alternative dimension Carcosa. Resulting in the formation of the Covenant of the Void and eventually technology to enter into other parallel dimensions. The War saw the first ever mass usage of cold fusion weapons on the field and the eventual complete destruction of most habitable land in Carcosa for human based life due to the mass usage of fusion weapons resulting in land being irradiated beyond the ability to be terraformed and or completely glasses. The formation of the Covenant of the Void was born out of total necessity. By destroying their own habitable land, the survivors were forced to develop inter-dimensional travel just to survive. This creates a powerful motivation for the Covenant: not for exploration but to find a new habitable dimension. The Covenant: The Covenant is an amalgamation of different races forced under the banner of Hastur being the winning faction of the Reclamation war. Most of these races were forced to join unwillingly and are forced into a state of total euphoria forced to be completely loyal under Hastur (who he himself is a powerful reality bender). A few races (the Carcosians who are essentially humans) joined Hastur willingly out of desperation. Other races who joined willingly are the cruel Cthyula (basically imagine Cthulhu but uh human sized and were just really strong reality benders) who joined purely because Hastur was winning in his invasion of Carcosa. Technology: Even before the Reclamation War Carcosian technology was highly advanced. From manipulation of higher dimension (no not time travel they had the ability to manipulate the W axis) however through out the war due to the warlords states constantly fighting and the exhausting of industries made the usage of such advanced weapons completely impossible and regressed Carcosas technology back by near a millennium. The Reclamation War: The War of Reclamation can be split into 3 phases: phase 1: all sides use 4th dimensional geometric weapons and highly advanced reality warping to essentially erase each other. However with industries being destroyed each side is forced to use less expensive weapons phase 2: With "clean" being essentially impossible to mass produce the factions resort to using older fusion weapons. These dirty weapons essentially use the power of fusion to power a large weapon that creates nuclear explosions.While proven powerful they were destructive to the environment. phase 3: with sides becoming desperate kinetic slug throwers from fast firing machine guns to literal matchlock and flintlocks are brought back into service. Religion: Shockingly enough the Covenant allows freedom of religion as controlling every race to follow a single religion or simply be all aethiest would be impossible. However it is well known the Hasturs inner circle is essentially a cult. NOTE: when I say cult I don't mean devil worship or worshiping Hastur as god. Hastur is similar to a god in power but isn't a TRUE god he's just a powerful reality bender. A cult is a social group or movement defined by excessive devotion to a charismatic leader, person, or idea, often employing unethical, manipulative, or coercive techniques of persuasion and control. They dont worship him like a god but are heavily devoted to him.
quick summary if you don't wanna read: The Void Covenant is a Stalinist/Totalitarian regime draped in the skin of a Lovecraftian horror story that happened because a bunch of dudes wanted to rule Carcosa screwed up the environment and industry to unhinged levels. The end.