The Underkeep of Greb-Bithan
The Underkeep, or Underfort of Greb-Bithan was built in ancient times by dwarves, in the early days of remembered history when most dwarves still lived deep underground. The structure was originally created deep underground, near the high reaches of the underdark, and then excavated further upward. When the dwarves reached the surface, they created a small fortress and gathering hall to guard their access point to their homeland.
Thousands of years later, the deepest reaches of the Underfort were intentionally collapsed and sealed against access from the Underdark.
This bought the dwarves some time, but within two centuries, they were driven out of Greb-Bithan entirely by a race of serpent people, who took over the underground structure for themselves. Little is known about the brief period the serpent people held the Underfort, but the Dwarves of Heligastenen never returned, and consider the place cursed and haunted.
The Underfort is a three-day hike north of the town of Llangelynin, centrally located in the southern region of Heligastenen.
The artifact known as the Dragon's Tooth Codex revealed that an otherworldly force guards the Orb of Palantha-Kawon in the deepest reaches of the Underfort of Greb Bithan.