Complex sentence: Though he is a Maiar, specifically he is apart of a sub group of Maiar that were fiery spirits known as the Valaraukar and on Middle-earth and to the children of Iluvatar, the Valaraukar are known only as Balrogs.
Split into simpler sentences: Though he is a Maiar, specifically he is apart of a sub group of Maiar that were fiery spirits known as the Valaraukar. On Middle-earth and to the children of Iluvatar, the Valaraukar are known only as Balrogs.