Spirit Realm

Many universes had Spirit Realms connected to them, which were a natural destination for various spirits if they were not directed to more substantial afterlives. The walls between a given Spirit Realm and its matching physical universe were weakened every Halloween.

The Prime Universe's Spirit Realm was an intangible void. By the 2010s, due to an unidentified threat, the Great Ghost believed it to be “doomed” and was looking for a way for him his legion of spirits to permanently escape. He intended to do so via ordinary spirit paths, but, when Frankenstein-818's malfunctioning Spirit Realm Gateway opened a Rift between the Spirit Realm and the Cupid Homeworld, took his chance and led his legion out of the Realm through that portal. While the spirits rampaged, looking for bodies to possess across the Multiverse thanks to a flotilla of Fog Ships stolen from the Cupids, Frankenstein built a One-Way Forced Spirit Realm Gateway which, when activated, would send everything around it to the Spirit Realm.

However, before he could use it, Frankenstein was abducted by the spirits and forced to build a Reverse Spirit Realm Gateway to replace the Rift, which the Department of Rifts had sealed. After a short mishap with the One-Way Gateway where Foreman-964, Pythagoras-858, Technophile-963, Igor-1612 and Philatel-426 were briefly transported to the Spirit Realm before being summoned back by Juliet-178 using the reverse switch of the One-Way Gateway, the Cupids managed to send most of the ghosts back to the Spirit Realm. When they tried to return through the Reverse Gateway, they were transformed into clockwork toys of which Madame Tarsa took possession. The Great Ghost, meanwhile, was separated from his host body and sent to parts unknown. (PROSE: The Ghosts and the Machine)

the Frost King primarily resided in a Spirit Realm. In 2021, it had apparently become lonelier than it normally was. (PROSE: The Winter Quests)