Tolkien was a devout Catholic but also had a love of Anglo-Saxon mythology from the days predating the Norman invasion. The “theology” of Middle-earth was his wish to blend the two. In his universe, Eru/Iluvatar is analogous to God. While the Ainur (Valar and Maiar) are analogous to angels, but function in Middle-earth like polytheistic gods of mythology. As Eru allows for “sub-creative” power in a limited way to each of the Ainur.