Hell-hawk
The Mountain of Fire#36 (x2/x1)
Treachery
Morgul.  

When Revealed: Either search the encounter deck, discard pile, and victory display for a Nazgûl enemy and add it to the staging area, or attach Hell-hawk to a Nazgûl enemy in play. (Counts as a Mount attachment with the text: "Limit 1 per enemy. Attached enemy gets +2 , +2 , +2 and is immune to play card effects.")