J.R.R. Tolkien’s Gandalf fights a Balrog on the Bridge of Khazad-dûm.
The confrontation occurs during the Fellowship’s escape from Moria in The Fellowship of the Ring. The Balrog is an ancient being of fire and shadow that awakens in the depths beneath the dwarf kingdom. It pursues the company to the Bridge of Khazad-dûm.
Gandalf prevents the Balrog from crossing the bridge, but both fall into the chasm. Their struggle continues beneath the mountains and ends at the peak of Zirakzigil. Gandalf dies in the battle, then returns as Gandalf the White.
The Balrog is not a dragon, although both are powerful creatures associated with fire. Tolkien’s legendarium identifies Balrogs as corrupted spirits of the same broad order as the Valar and Maiar. The singular form “Balrog” names the type, while “Durin’s Bane” is the title given to this particular one.