What is the name of the Balrog that appears in Moria?

The Balrog that appears in Moria is known as Durin’s Bane. It is an ancient fire-demon who survived the overthrow of Morgoth at the end of the First Age and hid deep beneath the Misty Mountains for thousands of years.

The Dwarves of Khazad-dûm awakened it while mining for mithril during the Third Age. The creature killed King Durin VI, giving rise to its name, and later killed his son Náin I. The surviving Dwarves abandoned their underground kingdom, which became known as Moria, meaning the Black Pit or Black Chasm in Sindarin.

Durin’s Bane is not a personal name like Smaug or Glaurung; it is a title describing the monster’s connection to Durin’s royal line. Gothmog was a different and especially powerful Balrog who served Morgoth in the First Age. In Moria, the creature battles Gandalf on the Bridge of Khazad-dûm and finally at the summit of Zirakzigil.