Pyramid of Shadows
The Pyramid of Shadows is an eternal prison that moves around from dimension to dimension and ignores time and space. People on the inside of the prison age at in infintessimal rate and require no sustenance to live. Some choose to eat out of habit however. Furthermore the inside of the pyramid morphs and changes to suit its currents inhabitents. The walls, ground, ceiling, and items on the inside of the rooms of pyramid change gradually to suit the needs of the creatures that live within it.
There is a dim light radiating unnaturally from evreywhere within the pyramid undoubtedly some sort of supernal magic.