The Lord of the Rings: Shadow of the East
Balrogs, called Valaraukar in Quenya, are fallen fire spirits who once served the Valië Vána. Seduced by and perverted by the Black Enemy, the Balrogs served as the chief war-lords of Angband. They also comprised Morgoth’s elite guard. Details of their numbers are hard to state with certainty, but there seem to have been relatively few of them – probably no more than seven.
In appearance, the Balrogs are man-like, but fire stream from them, and they are swathed in dark shadows. They carry whips of flame and induce great terror in friends and foes alike. In the War of Wrath, Morgoth was assailed by the forces of the Valar. Most of the Balrogs were destroyed in that War, but some few escaped over the Blue Mountains and hid in Middle-earth.