[Nerwen]

IARWAIN BEN-ADAR it is!

"Ben" means "son of" in Hebrew (don't know about Arabic, but they're related). However, I guess that's a coincidence, as BEN-ADAR means "fatherless" in Elvish, where the "ben-" element must mean "without".

NAMELESS THINGS: Earth's anonymous gourmands.
SILENT WATCHERS: Mordor's misnamed alarms.
IARWAIN BEN-ADAR: Bewildering- me, in a conflict? What would my dad say, if I had one?
GOTHMOG: Emo feline at the Pelennor.
WERE-WORMS: ...but are they worms now?
UNGOLIANT: Emaciated king of beasts confused for even more ravenous predator.

Now you just have to work out what all these persons, beast and monsters have in common.

Edit: x'd with Huey. Correct on the theme. They're all beings of unknown nature. The password expresses this concept.