I've finally beaten RTM Nightmare in pure solo.
Not a new deck, it's a power deck we've seen around, but this quest is so unbalanced and nasty for solo play that I had to tweak the deck.
You have to be lucky with the encounter deck, so it's almost purely a matter of luck (that's why I say that's it's unbalanced).
It took me 12 tries with this deck!
If you did it with another deck, I would like to know!!!