Grand Unifying Guesses/Dark World

The following are all the same place:

 * Hell, obviously.
 * The Warp
 * Hueco Mundo
 * Minusland
 * The Minus World
 * The alternate hotel from Trilby's Notes, also known as the Realm of Magick/Realm of Chzo
 * Yami-gaia
 * Shinigami's World
 * The Demon World
 * The Twilight
 * Times Square during the 1970s and 1980s
 * The dark side of Imaginationland
 * The Ghost Zone
 * The Spirit World
 * The Spirit World
 * The Phantom Zone
 * The Phantom Zone, again
 * Dollurh
 * The Dark World
 * The Gap Between Dimensions, where Phantom Ganon was sent.
 * The Home For Infinite Losers
 * This place has a lower vibe than the Realground
 * The Netherworld
 * The Shadow Realm
 * The Shadowlands
 * Ghost World in the 2009 game
 * The Dungeon Dimensions
 * Todash
 * But, Todash isn't a world while the places listed above are.
 * Zimmy's world
 * A number of places in the Digimon franchise, including the Dark Area, Dagomon's Ocean, and the dimension in which the D-Reaper evolved.
 * London Below
 * The Dark Hour
 * The Otherworld/Midnight Channel
 * The Otherworld
 * Otherworld and its various layers
 * The Otherworld.
 * The Dark Realm
 * The Spectral Realm
 * The Realm of Darkness
 * Valhalla
 * The Netherrealm
 * Hotel California
 * The Barren Landscape of the Demon-Beasts.
 * The Boundary
 * Shadowfell, Shadowdark, Darkbad, Shadow Shadow Bo Badow, Double Hell and Scarytown.
 * And all of these places are 'Soft Places' as described in The Sandman, where the boundries between reality and the Dreaming are weak.