Nacreum
The Nacreum is a transdimensional prison composed of intelligent nacre (nonfiction).
Description
The Nacreum was built to hold slippery characters such as The Eel.
Mobility
The Nacreum can travel quite widely in time (nonfiction) and space (nonfiction)
It does this independently of Abalonia, which has similar abilities.
This time-space travelling ability is presumed (by whom?) to be some form of the Gnomon Algorithm.
Spider-Man (nonfiction)
The Nacreum would be delighted to confine Spider-Man (nonfiction) for an issue or two.
This offer is contingent upon Marvel Comics (nonfiction) and myself (nonfiction) (as the Nacreum's agent) agreeing to terms beforehand.
Abalonia and Gnotilus
The Nacreum is (usually) located in Abalonia.
Gnotilus, the founder and first citizen of Abalonia, keeps many of his prisoners in the Nacreum.
Euphoriolanus
Euphoriolanus occasionally gets himself committed to the Nacreum for what he he calls "a bit of recreational incarceration."
Fiction cross-reference
Socrates could have saved himself by accepting imprisonment in the Nacreum; but he preferred to die the Athenian way.