[Belegorn]

I should mention there were spirits of fire who joined Melkor. Glorfindel did defeat one and his companion Ecthelion defeated their Chief, Gothmog at the King's fountain. Both were killed as well but Glorfindel could have lived after defeating his Balrog. It happened to drag him down into the chasm with him as it died. In fact it seemed Glorfindel overpowered this balrog. So I might say there were few Elves of this class and they were probably pretty close in power to the lesser Maiar. So Glorfindel did find himself the equal of a Maia and I think the Balrogs were such as the Maia who drives the sun is also a spirit of fire.