Demonic spawn from a underground collective of bunkers, caves, and tunnels gone wild with bio-engineering. Not FEV level but based around psuedo-CRISPR, mad scientist stuff. Centaurs already look like a hell beast, mind. '
Drawing from my 'New Monsters' post, and a bit of Edward Sallow, the guy who found this comes across some pre-war books - Might is Right, maybe, the Ars Goetica, stuff like that. Maybe they're a disgruntled scientist from some post-war university, or even a monastery such as The Abbey, and they fall off the deep end - maybe their university was burned to the ground by a religious group or idiotic bandits, and they swear to bring 'hell on Earth' or something.
Inb4 'Oblivion with Guns'/'Doom Knockoff', but eh. I wanna kill more Devils and Demons and Imps and Daemons and Fiends. The guy goes into a Vault and transforms it; and decides that in this brutal world, humanity has to adapt and face trial after trial - throwing in a bit of the Master and Unity in there - with changing mankind into radiation resistant psuedoSocial Darwinists, inspired by Demonic influences.
(By Barlowe)
Of course overall it's basically the worst kind of horde; that goes around, burning and looting and butchering, full of intercine strife, held only together by strongmen following strongmen following strongmen - feeling a bit of Wesnoth Orc influence here - of course it's not monolithic, some groups see value in discipline and cooperation to get something more than the sum of their parts, maybe forming a 'Revisionist' clique within the faction, while others are far more shortsighted, if they can see at all - a lot of sub-sapients and morphed animals are used, too.
But yea out of nowhere into this batch of squabbling communities and pre-war groups like the Military (not Enclave, as in, USM gone local) and the like, BAM. Demonic Horde, burning settlements, setting up fiefs, fighting everything.
(By Noxiihunter)
Could really be a threat to unite the region around, unlike the shit we got with the Institute. Could also be tempting - after all, isn't the player basically a walking testament to their ideology? Unless the diplomat actually manages to scrounge together an army to fight for them to get to the big bad to talk them out of their worldview, or sneak in a grenade to his vault throne room....
Oh sure it can get more edgy than serious real fast, so maybe a lot of the outright 'Satanist' stuff could be toned down. Not a lot of pentagrams or sigils every which way, Caesar had a bull, maybe this guy has a Goat flag and little more.