Narbondel

Narbondel is the only unshaped piece of stone within the boundaries of the cavern. The people of the city use it as a clock. Each morning, around midnight, the Archmage of city casts a fire spell at the base of the rock pillar. The heat from the spell forms a band around it and moves up, taking twelve hours to reach the peak, before travelling down it again, going out once it reaches the base.