Tyar-Besil

Tyar-Besil was the ancient fortress-city of the shield dwarf kingdom of Besilmer, built around -4320 DR under the Sumber Hills in the Dessarin Valley. It was eventually overrun by hordes of orcs, trolls, and giants.

Founding and fall
Although the dwarfs of Besilmer had, in -4420 DR, settled overground under the leadership of Torhild Flametongue, they suffered constant attack from trolls and giants, which led to the construction of the underground fortress city of Tyar-Besil around -4320 DR.

Torhild Flametongue was killed in combat against a hill giant at Stone Bridge, and this led to the fleeing of the dwarves in the area, and later, to the complete abandonment of Tyar-Besil by -4160 DR.

Rediscovery
Tyar-Besil was rediscovered in 893 DR by an adventuring company called the Knights of the Silver Horn. Over the subsequent six years, the adventuring company continued to return to the ruined city, and were able to construct strongholds at the hidden entrances to Tyar-Besil in an attempt to protect it.

When the orc realm of Uruth Ukrypt gained power, leading to the Orcfastings War, the First and Second Trollwars, and drow raids, the human population of the Dessarin Valley was almost wiped out, and the Knights of the Silver Horn had disappeared. Their former strongholds, protecting the hidden entrances to Tyar-Besil, became known as the Haunted Keeps.

15th century
The fortress-city was later used as a base for the Cult of Elemental Evil in 1491 DR.