Narbondel

The Narbondel is a huge stalagmite in the city of Menzoberranzan. It also is the clock of the city. At the end of every day the archmage of the city, currently Gromph Baenre, casts a fire magic upon the stone to heat it. This heated point climbes the stalagmite during the day and shows the drow the passing of time. At the end the stone glows in red before it cools down rapidly and the archmage renews the magic. This darkening of the Narbondel is called "Black Death of Narbondel".

Tomb of Menzoberra
Besides being the clock of Menzoberranzan the stone pillar houses a much greater secret. Within the stalagmite the ancestors build the tomb of the legendary founder of the city itself, Menzoberra the Kinless. From a top of the pillar leads a secret stair 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. It was the drow Zaknafein Do'Urden who found she there and took the Dagger of Menzoberra to bring it back to the city. After he did this the spider's web crashed and the cocoon with the corps fell into the depth.

Literature
2. Edition: Romane: Narbondel
 * War of the Spider Queen.