[[WMG: The Doomsday World is a fusion of all worlds that have ended or are about to.]] The End of the World isn't just a time, it's a place. The Valley of Megiddo. The part of the multiverse that's circling the drain. Thus, any world that ends fuses with it, with the [[Main/{{ZombieApocalypse}} Zombie Apocalypse]] waiting for them. This is why Bok Zombies can respawn, defeat one, and eventually a timeline where it wasn't killed manifests. This also means that worlds that are in critical danger of ending have a very thin dimensional wall, hence the worlds of ''[[Main/{{MegaManBattleNetwork}} Mega Man Battle Network]]'' and ''[[WMG/MetalGear Metal Gear]]'' have had incursions.
* [[WMG/MetalGear This also explains Vamp.]]

* For a brief period of time, [[Main/{{TheHeartless}} The Heartless]] of Xehanort from ''[[WMG/{{KingdomHearts}} Kingdom Hearts]]'' made his base here. "The End of the World" after all.
* Also, the entirety of ''VideoGame/HellgateLondon'' takes place there with the human "survivors" still battling the demonic and undead hordes out of a mistaken belief that their world still exists and can be saved.
* The abyss from FromTheAbyss is either the Doomsday World itself, or a tunnel leading to the Doomsday World.

[[WMG: Dark Matter is a form of Main/{{Nanomachines}}]]
Oh, there's a lot of psychic/spiritual energy involved, but ultimately the Immortals are just the remnants of Main/NeglectfulPrecursors who believe their own mythology. It's latched onto Dark Energy as its power source, which is why Sunlight can destroy it.
* As ''VideoGame/MetalGearSolid4'' shows us, nanotech can do a ''lot''.
[[WMG: The world of Boktai is the [[Main/{{AfterTheEnd}} aftermath of the apocalypse]] in the Mega Man Universe]]
This would explain the SchizoTech. An advanced solar-powered gun, connections to Battle Network's net, a bank with computer terminals, and a huge and apparently quite complex clocktower all exist in an apparently medieval setting?
[[WMG: Galaxy Universe/The Will of the Galaxy was formed from remnants of [[Franchise/SailorMoon Sailor Galaxia]]'s Chaos-afflicted energies.]]
* Her compassion was twisted by the energies of Chaos: in an attempt to free the Universe from Death, it became Klorofolun, which causes Undeath.