The upped version still costs the same as unupped
Also, this screams "mindgate"
Maybe I'm off but here's how I see it playing potentially:
Have Mindgate in play, use "Forward" to put one Nightmare from your hand on top of opponents library, use Mindgate to get it back after putting it there, playing the Nightmare thus keeping them from drawing the Nightmare you just put on their deck. Rinse and repeat. Lock down.