If this were my campaign, I know where I'd put it. On Carceri, in the Bastion of Last Hope, stands a featureless warehouse with no windows or doors. The eyes of passersby tend to just slide right past it. This is the House of Oblivion, the place where lost and forgotten things go. The inside of the House is much larger than the outside, and might actually exist on a separate demiplane. The place is filled with piles of lost and forgotten trash, treasure, artifacts, and memories. The ghosts of those whose memorial stones have faded away dwell here, as well as the shadows of forgotten events. The aura of residual magic has spawned many Huge and Gargantuan raggamuffins.
The real trick is, though, that nothing can get in unless it is lost or forgotten. No gate will open there, no crystal ball will scry inside. Players will have to figure out how to get hopelessly lost, and hope that everyone they know stops thinking about them.
Thank you!
