Narbondel

The Narbondel was a huge stalagmite in the city of Menzoberranzan and served as a clock for its inhabitants.

History
At one time, the drow Zaknafein Do'Urden found Menzoberra's tomb within Narbondel and took the Dagger of Menzoberra back to the city.

During the Time of Troubles in 1358 DR, the clocktower was bathed in searing flames that blinded those who looked upon it with darkvision.

Structure
Narbondel was the only unshaped piece of stone within the boundaries of the city cavern and it was used as a clock. At the end of every day, the Archmage of Menzoberranzan cast magic upon the stone to heat it. The heat from the Archmage's spell formed a band around it and moved up. When the end of the glow was at the pillar's top, the day was almost done. When the pillar was completely dark, it was called "Narbondel's Black Death" (effectively midnight).

Tomb of Menzoberra
Besides being the clock of Menzoberranzan, the stone pillar housed a much greater secret. Within the stalagmite, the ancestors built the tomb of the legendary founder of the city itself, Menzoberra the Kinless. From the top of the pillar, a secret stair lead to the hidden chamber where the body of the priestess once lay in a cocoon upon a huge spider's web spanning a tremendous abyss. When Zaknafein took the Dagger of Menzoberra, the spider's web crashed and the cocoon with the corpse fell into the depths.