Verbal Reasoning!

[Mettare]

Reverse mood for the second set.

The opposite of hope should be despair. But I wouldn't think that the Valacirce brought despair. Of course, it might have brought despair to the evil side.

Both pairs contain one article of jewelry and one thing that appears in the sky. Though I switched the order of their appearance in the pairs. The sets are opposites, after all. Or as close to opposite as I could make them.

OK, I'm going to guess the missing piece of jewelry is the One Ring. Because, as the Valacirca kind of signalled the downfall of Morgoth, the One Ring destroyed Sauron in the end.

Bad guess, I know.