[Annatar!]

I also agree that 'nursed' is so evocative. The juxtaposition of terminology that seems nurturing, wholsesome and good with the horror.
This juxtaposition is emulated in his characterisation of the actual agents of evil. Tolkien often shows a great respect for the darkness in all of the ME books, he endows it with, what are essentially, positive terms; Smaug The Golden, Shelob The Great, the most terrifying of the Nazgul is their 'King", the most terrifying of the Balrogs is entitled 'Lord'.
The second Dark Lord of ME creates his greatest work in a guise of fairness (as Annatar), the first Dark Lord is said to have received the greatest gifts of knowledge and power from Illuvatar.
He uses these terms to signify their importance as the elements of evil?
If something is a lord or a king of evil then it must imply a greatness of terror and horror.
Perhaps some of the effect of the horror of these creatures/ characters is that they are held by the author in some form of reverence, and in the context of the story often fell from a place of reverence.
To fear what once was good (i.e Balrogs, Nazgul, Sauron, Ocs, Uruks) illustrates the true horror of the corruption of Morgoth.
IMO the scariest and most horriffic element of the entire history of Ea is that first discordant note that Melkor uttered, one moment that caused all that is corrupted to be interwoven into fate, and the fact that the note is still resounding even after the servants of that chord are gone.