Tolkien's conception of Balrogs changed over time. In all his early writing, they are numerous.
A host of a thousand of them is mentioned in the Quenta Silmarillion,[11] while at the storming of Gondolin Balrogs in the hundreds ride on the backs of the Dragons.[12] They are roughly of twice
[13] human size,
[14] and were occasionally killed in battle by Elves and Men.
[15] They were fierce demons, associated with fire, armed with fiery whips of many thongs and claws like steel, and Morgoth delighted in using them to torture his captives.
[16] They were loyal to Morgoth, and once came out of hiding to save him from capture.
In the published version of
The Lord of the Rings, however, Balrogs became altogether more sinister and more powerful.
Christopher Tolkiennotes the difference, saying that in earlier versions they were "less terrible and certainly more destructible". He quotes a very late margin note
[17] that was not incorporated into the text saying "at most seven" ever existed;
[18] though in the Annals of Aman, written as late as 1958, after the publication of The Lord of the Rings, Melkor still commands "a host of Balrogs".
[19] In later writings they ceased to be creatures, but are instead
Maiar, lesser
Ainur like Gandalf or
Sauron, spirits of fire whom Melkor had corrupted before the creation of the World.
[3] Power of the order of Gandalf's was necessary to destroy them,
[20] and as Maiar, only their physical forms could be destroyed.
