Master of Sauron

[kittiewhirl1677]

Please forgive me if a similar thread exhists, but I couldn't find one.

I got the idea for this thread after reading this phrase in RotK, The Last Debate(said by Gandalf):

Other evils there are that may come; for Sauron is himself but a servant or emissary. Yet it is not our part to master all the tides of the world, but to do what is in us for the succour of those years wherein we are set, uprooting the evil in the fields that we know, so that those who live after may have clean earth to till. What wether they shall have is not our to rule.

My focus is on the first part:

Other evils there are that may come; for Sauron is himself but a servant or emissary.

Who do you think Tolkien was talking about here? Is there any mention of it anywhere else, in his other books? It's just strange, to think that someone so incredibly powerful could have an even MORE powerful master, and that master could have an even MORE powerful master and so on, and so forth. But the pupose of this thread is just to discuss any evidence of there being someone higher in status than Sauron at the time of the War.