Necrocracy

A Necrocracy is one of the weirdest possible government systems, and one that can only really function in a fantasy setting. To put it bluntly, this is a government in which power is held by the dead - or, in fantasy, the undead. This may be a single kind of undead, typically a lich, mummy or vampire, or it may be an array of different undead creatures. The point is, if the ruler is undead, then it's a necrocracy.

The Three (Four) Types

In the real world, a Necrocracy is a government in which the formal leader still holds power, despite being dead. The only example of this is North Korea, where Kim Il-sung is still formally considered to be the guy actually running the place despite being long dead. In fantasy, where undeath is a thing, necrocracies are more practical, and come in three recognizable types:

• Total Necrocracy: A true "kingdom of the dead", this is a necrocracy because everybody is dead here. The most iconic example would be a lich or mummy ruling over a city populated entirely with Walking Dead, or a massive clan of ghouls, or even a haunted ruin still inhabited by ghosts.
• Rule of the Dead: Largely associated with vampires, this is a necrocracy in the most classic sense; the ruling caste is undead, but the commoners they rule over are still alive.
• Half-And-Half: Sitting in between the two models described above, this is a necrocracy with undead rulers reigning over a mixture of undead and living subjects.

List of /tg/ relevant Necrocracies

Magic: The Gathering has the Grixis shard of Alara (where all who hold power are either undead, demons, necromancers, or any combination thereof), and the Orzhov Syndicate and Golgari Swarm of Ravnica as prominent examples. Innistrad is known to hold villages ruled over by vampire nobles, and in the Conspiracy core set, Fiora is ruled by the ghost king Brago, and the custodi are a semi-theocratical church oriented towards spirits.

Warhammer Fantasy has Sylvania, the realm of the Vampire Counts (Half-and-Half) and the Tomb Kings of Khemri (Total Necrocracy). Nagash also wanted to turn the world into a Total Necroracy, but the best he achieved was taking dominion over the Half-and-Half Realm of Shyish in Warhammer: Age of Sigmar.

In Warhamer 40,000, the Necrons are a cross between a robot empire and the Total Necrocracy version of this, being the uploaded minds of an alien race transferred into corpse-like cybernetic bodies. The Imperium technically is an example of the real-world version of a necrocracy, since the absolute ruler is the God-Emperor, who is a corpse in pretty much every little detail.

Dungeons & Dragons could have its own personal list, that's how often this shows up:

• The realms of undeath-related deities such as Vecna, Orcus, Kyuss and Kiaransalee typically follow this aesthetic.
• Dragon Magazine #383 featured an article that discussed how DMs could build necrocracies of their own using the city-building mechanics from the Dungeon Master's Guide II, and featured the Oligarchy of Mavet Rav as an example. These rules and the details of Mavet Rav can be found freely online [here].
• In Eberron, you have the Deathless of Aerenal, which are basically undead ancestors that serve as a kind of gestalt-deity to avoid subjecting ancestors to Dolurrh. There's also the Half-Dragon Elf Lich Erandis Vol, who wants to conquer the world, and Karrnath, which is unknowingly ruled over by a vampire.
• After the Spellplague, the lich of Szass Tam turned Thay into a necrocracy where liches ruled over the wizards who traditionally ruled the former magocracy.
• In the Nentir Vale setting, the fallen empire of Rahesh was a necrocracy in which the living and the undead lived as equals and where necromancy was openly embraced; it faced and annihilated countless assailants, but was ultimately destroyed by volcanic eruptions.
• Many Domains in the Demiplane of Dread are limited "Rule of the Dead" necrocracies, with a singular undead monster as the reigning power of the domain, due to it being the resident Darklord.
• In Golarion, the nation of Geb is a Rule of the Dead type necrocracy where the division between "living" and "undead" is synonymous with the division between "peasant" and "royalty". It's unusual in that it's a highly multi-"racial" nation, with many different kinds of undead residing there, including ghosts, mummies, liches, ghouls and vampires. In contrast, the city-state of Nemret Noktoria in Golarion's Underdark is a nation of ghouls.
• Midgard has its own Underdark ghoul empire, where a unique strain called the Darakhul reign over multiple subbreeds of ghoul and ghast.
• In Grim Hollow, about two thirds of the Ostoyan Empire are ruled over by vampires.
• In the Arkadia setting, the Dark Elves of Nys are ruled over by mummy witch-priests of the undead Titan known only as "The Worm".

Exalted, thanks to the nature of the Underworld, means that the dead and the living can often intermingle. The necropolis of Sijan, City of Ten Thousand Tombs, is ruled by its ghosts, who are relatively benign. The Deathlord known as the Silver Prince runs a flourishing kingdom by reanimating corpses to serve as slave labor — but it's a cover for his long-term evil plans. Thorns became this when the Mask of Winters invaded and pulled it into the Underworld. Now zombies and ghosts roam the streets and the living are second-class citizens. The Resurrectionists in Autochthonia want to make Claslat into one of these...for the greater good, of course. They just have no understanding whatsoever about the nature of undeath.

The realm of Cryx in Iron Kingdoms, whilst technically ruled over by the dragon Toruk, has upper echelons largely made of artificer liches and makes heavy use of bone-and-metal steamjacks for its troopers, supplement by cyborg zombies.