Operation Crypt Slayer is a personal worldbuilding project of mine that I have been working on for quite some time. It involves a world war between all of humanity against Vampires and their vast inexorable horde of fodder subsequently after the end of World War 2. The following main factions within the story itself are the following:
The Vampires themselves:
Immortal powerful undead beings that have existed for eons in the world of darkness. Having preyed on humanity and gained societal influence before deciding to use this power to enslave humanity as part of a grand and terrifying ritual to ascend to godhood. With the power to slaughter entire human armies by themselves, the Vampires have confined themselves to their towers and interdimensional fortresses and usually just assign their monstrous minions to do most of the combat.
The Soviet Union:
Following the end of World War 2. The Soviet Union unleashes the wrath of their secret technological arsenal upon areas afflicted by the Vampires. Forced to fight across miles upon miles of blighted land corrupted by unholy magics and twisted by otherworldly phenomenon, the Soviet Union fights a bitter war against the Vampires that continues to mount more and more bodies upon their side. Each and every day, the western front of the Soviet Union costs the lives of thousands of men and women serving to defend their homeland from the emerged Vampiric threat.
The United Global Defense Coalition:
Remnants of secret societies shattered and torn apart by the astonishing betrayal by their Vampiric masters. This secret cabal of immortal and wealthy individuals rule over the military might that is the United Global Defense Coalition. The United Global Defense Coalition oversees the entire North American continent, the Pacific, Africa, and South America. The United Global Defense Coalition now battles a plague of undeath on the African continent and a horde of monstrous giants in central Asia.
The Rattler's Insurgency:
Those that have taken up arms in their own homes that are now corrupted by the powers of the Vampires. The Rattler's Insurgency roots extend back to the ancient Penridge Academy. Their travels towards other realms have brought back artifacts from worlds left devastated by the Vampires in past conflicts, but their small size makes them unable to fight direct fullscale conflicts lest they risk being annihilated.
The Templar Ascendant:
Renegade and outcast Angels that have come to teach humans the art of death dealing and combat. The Templar Ascendant have come to guard the last vestiges of humanity in Europe from the influences of the Vampire and demonic in the area. These Ascendant Knights are few and far between in the ranks of the order, but their power and martial skill has enabled them to face down even the greatest of Vampire Lords.
Penridge Academy:
A mystical academy with its roots dating back to the mystical land of Avalon. Penridge Academy seeks to protect the Rune-Marked from the claws of the Vampires as the blood of mystically endowed humans enables a Vampire to gain a voluminous amount of power. Power capable of shattering city blocks and even scaling to the level of a Vampire Lord as if they had drank the blood of thousands of humans. Penridge Academy allies itself with the United Global Defense Coalition in the defense against the Vampire, even if their kind are subjected to being little more than experiments for the UGDC.