When was the last time you used this card? Yeah, almost never, maybe for fun, but that's about it. It is a counter to Fractal, and nerfing Fractal therefore indirectly nerfs Nightmare.
I think this card should be buffed, not sure how, but it's not much use as is. My thought was to maybe to let it add Relics to the opposing hand, instead of targetting a creature. After all, this way you'll be sure your opponent won't play them and right now, decks based on Nightmare have a serious risk of the opponent being able to play the target creature anyway (not to mention you need to have that creature on your field first, too!).