What is the name of the fiery demon in The Fellowship of the Ring?

The fiery demon in "The Fellowship of the Ring" is known as Balrog. Specifically, it is referred to as Durin's Bane, a powerful creature that dwells in the depths of Moria and confronts the Fellowship during their journey through the Mines. The Balrog is a shadowy figure engulfed in flames, wielding a whip of fire. Its encounter with Gandalf leads to an epic battle on the Bridge of Khazad-dûm.