Also known as: The Balrog Of Moria
One of the Balrogs of Morgoth -- a Maia of fire seduced by the first Dark Lord in the deeps of time, clothed in shadow and a mane of flame, and armed with whip and sword of fire. When Morgoth was overthrown at the end of the First Age and his fortresses broken, this demon escaped the ruin of Thangorodrim and fled east, hiding for long ages in a deep place beneath the roots of the Misty Mountains, under the great Dwarf-realm of Khazad-dum.
In the year 1980 of the Third Age the Dwarves of Moria, delving ever deeper in their hunger for mithril, broke into its hidden deeps and woke it. The Balrog slew King Durin VI -- whence its name, Durin's Bane -- and the next year his son Nain I, and the terror of it drove Durin's folk from Khazad-dum, which thereafter was named Moria, the Black Pit. For more than a thousand years it brooded in the dark, until the Fellowship dared the Mines and Gandalf met it upon the Bridge of Khazad-dum, denying it passage. Still locked together, wizard and demon plunged into the abyss, and their battle ranged from the deepest dungeon up the Endless Stair to the peak of Zirakzigil, where after a long and terrible struggle Gandalf at last cast down his enemy and himself died of the labour, only to be sent back to finish his task.