Although there is certainly nothing quite like Tolkien’s sub-creative, demiurgic Valar to be found in the otherwise extensive and speculative angelological reflections of St. Thomas Aquinas (the “angelic doctor”), there is, I think, a very interesting and suggestive similarity in the metaphysical and anthropological functions that these spiritual beings play in the respective philosophies of these two thinkers. For St. Thomas, according to Howard Kainz (Active and Passive Potency in Thomistic Angelology), speculation over the angelic nature had real value both in terms of its theoretical truth and its anthropological implications. In terms of Thomas’s overall theory of being, for example, Kainz makes the case that
a philosophy of the angels is of prime importance for throwing light on the “nature of contingent being.” When we try to apply the categories of essence/existence, act/potency, substance/accident, etc., to the complexities of composite creatures, our discussion often becomes impeded because of the introduction of multiple contingent factors. But if it is within our power to discuss the same categories in relationship to a state of “pure” creaturehood beyond space and time, we should be able to get more easily beyond obfuscating tangents to grapple with the problem of the truly necessary relationship between essence, substance and accident, etc.
As simultaneously created and hence contingent yet immaterial beings, in other words, what angels represented for St. Thomas are an extraordinarily unique instance of the creaturely act/potency and essence/existence distinction, unique because it occurred apart from or without any corresponding form/matter distinction. Put plainer still, angels represented a distinct metaphysical possibility (indeed, reality) that was at once explicable in Aristotelian terms and yet were a possibility and reality of which Aristotle himself seems to have been entirely unaware.
The Flame Imperishable 