Tomb Tapper Tomb

The Tomb Tapper Tomb was a demiplane filled with innumerable magic treasures with an entry portal somewhere in the Buried Realms region of the Lowerdark beneath Anauroch.

Description
The tomb itself was an enormous 2 mile (3.2 km) wide and 0.5 mile (0.8 km) high chamber lit by a dim gray light. Gravity was nonexistent in this space and the flow of time was erratic and unpredictable relative to the outside world. The air was said to be stale and poor in quality. Magic followed a similar detriment, with even the most basic of spells becoming incredibly difficult to cast when within the demiplane. Tomb tappers were faced with the opposite effect and thereby their magic was enhanced as long as they were within this realm.

Slowly floating through the gravity-free void were over a dozen castles that doubled as vaults for magic items stolen from all across Faerûn by the tomb tappers. Each of these castles were ringed by thousands of orbiting boulders. These boulders could be manipulated with spellcasting to create temporary bridges between fortresses.

There were so many magic items present in the vaults that not even a portable hole or bag of holding could contain them all.

Geography
The tomb was located in a demiplane created by the very same Netherese arcanists that created the titular tomb tappers. The only way to access the tomb was through a portal deep within the Lowerdark beneath the deserts of Anauroch. The portal would move up to a dozen miles to a new location every one to ten days, regardless of if that location was connected to a cave system or not, leading to it potentially being embedded in solid stone until its next change in position.

Inhabitants
The tomb contained a wide variety of powerful beings that would not let their treasure be taken easily. Treasure vaults themselves were often guarded by a dozen or more tomb tappers alongside various undead and constructs. All creatures guarding the vaults were incredibly hostile and would attack living intruders on sight, often calling for reinforcements from other castles within the tomb.

The most powerful being in the demiplane was the demilich known as the Keeper of Thaal. The Keeper was often seen with a small gathering of various undead under his command created from the deaths less fortunate adventurers, including the likes of liches and ghosts. The tomb tappers unerringly followed his command, so it was suspected that he was their true master.