>>75925435alright, going to try the short version, so in this setting an empire from another planet is given the ability to use portals to other planets and a unique artifact in order to indulge the sacred mission in the name of a goddess of conquest, it leads invasions on other worlds until it looks like sort of a blend of outworld made up of archetypical monster races, lead by orc warlords, and around 2030-ish, they do the same to earth, earth has higher tech then expected but they close the gap with a variety of magical assets, most especially the artifact that lets them, on a global scale, shift one sex to the other, so after twisting all of earths men into women, they make use of the ensuing panic and inability to fight a war of attrition against an empire worlds strong to make gains,
Humanity isnt out of the fight yet, making androids and forming alliances with defectors to hold back the tide, eventually a cabal of world leaders managed to make a deal with a powerful devil, who promised 1. an End to the invasion 2.destruction of the artifact and 3. a solution to the breeding problem. She fullfilled this promise by destroying the artifact, overloading it and making it turn everything across all the portal linked planets female, sealing the portals shut right after and then impregnating the leaders with the first Cambions/Tieflings.
So with survivors and refugees left to pick up the pieces, the first generation after are all half hellborn or half celestial thanks to angelic or demonic booty calls being used to fill thingsout before alchemists managed to find an optional herm brew or blessing from clerics etc.
its now 100 years later or so, and a number of cryo shelters that were formed on the very eve of the invasion awaken to a world without men, many of them former men themselves, peace or what of it there is is kept by new and revived knightly orders across the post apocalypcic magical landscape, questing about in power armor for chivalric glory