[Keeper of Dol Guldur]

To back up a little and respond to Voronwe, Thu, I think, was Sauron's name, because Sauron means "abominable one," or something similar, and he wasn't originally abominable or evil, so he probably only changed it or was called it after years of killing elves. And seven balrogs is a great number, if you talk about balrog captains, but boldog/balrog/daemon underlings is remarkably possible and would indeed whither to Manwe's power much easier than legions of Gandalf-slayer type Balrogs. By the way, they had wings.