Can you use the neutral Master Cards for the Saga version of the One Ring? Example playing black Riders and exhausting The One Ring on Frodo to play The Ruling Ring.

Nope. It says on page 3 in the rules for A Shadow in the East...

"Cards with the Master trait cannot be used when playing saga expansions."

That's what I would get for reading the rules right haha. Thank you

Do you think that rule still applies if you try to play a Saga expansion quest as a standalone quest (not campaign/fellowship mode)? That was the way I thought we could get "around" the rule. I was looking through all the quests the other day and I believe most of the quest cards don't reference playing The One Ring or Fellowship or anything like that.

I believe the saga quests, even when played outside the campaign, should be played with a fellowship hero (with the possible exception of the two POD quests that may be played in the saga). For example, in the first Black Riders quest, the treachery "Lure of the Ring" is part of the non-campaign deck, and explictly references The Ring.

That said, if you do wanna use that Master trait card with the saga One Ring, I think it's a good idea. Do it anyway.