Abaddon

Abaddon was the place where those below had their closest servants among the people of the Charry Mountain.  It comprised the surface fort on the mountain's face and the sub-structures that ran through the old mountain itself.  The surface fort's been the property of a succession of ruffians, bandits and the kind of mercenaries who favor red and black in their color schemes.  The underneath, well, there are a lot of entrances, some that come out pretty far from the mountain itself.  The first generation of explorers and would-be settlers sent people in to check out what had happened to Abbadon almost first thing.

They have since collapsed all the entrances they could find.  There is nothing in Abbadon.  No reason to go, nothing to be gained.  The people who went there had nothing, because anything you had that was worth having, you'd give up in a heartbeat to keep yourself out of Abaddon.  If you were starving, at least you starved in the open air.  If your babies were dying, be grateful they died in the sunlight.  You don't go to Abaddon.  They checked every inch of the place and found nothing you want to see.  If there are entrances from that place to the domain of those underground, they were entrances they wanted you to find and use.  Don't bother.  Undressed planks, hapazardly wedged into angles of quarried stone, ragged remains without names or means to identify.  That's all.

Abaddon was where the people of the region sent their worst and sent their weakest.  Calls for more were uncommon, but there was always a trickle, mostly criminals, but others, too.  People that could not be made to fit.  There was never a transfer station that was too far, and those who took the people below were always waiting, concealed in basket hats and bulky clothes that looked like they were made from wasp paper.  They took them below.  Anyone you sent to them, they took.

When the first explorers returned to the region, they came to Abaddon to see if anyone survived, because no one among the refugees claimed to escape.  No one ever did.  There's no point in looking.