Location from adventure-time by
A chaotic demon dimension beneath Ooo, ruled by Hunson Abadeer — a roiling hellscape of evil energy and demon bureaucracy.
The Nightosphere is where evil lives when it needs an address. It's accessible from Ooo through a ritual (say 'I hate you' to a picture of Hunson Abadeer and draw a smiley face in his dog food). Once inside, visitors find a dimension of absolute chaos run with the brisk efficiency of a mid-sized corporation. Hunson Abadeer manages the whole enterprise of evil from what amounts to a bureaucratic infrastructure, which is funnier and more disturbing than any other way the show could have played it.
A vast dark dimension of swirling chaos energy, populated by demons of every description. The sky is a permanent bruised purple; the ground is shifting dark matter; rivers of some terrible fluid wind through rocky demon-populated terrain. Hunson Abadeer's corporate-feeling office somehow exists in the middle of this chaos, complete with a desk and filing system.
Also known as: The Nightosphere, Nightosphere, The Demon Realm