I don't know much about EDH and was wondering if you could really cast {Nevermore} on your opponents commander. Seems overpowered.
Works, not really overpowered due to it's 1/99 in your deck, but it is perfectly valid and they would have to deal with it.
There are a lot of ways to destroy Nevermore, too. Green and white can easily destroy enchantments, blue can bounce permanents away or counter it, black has a few unconventional ways to deal with permanents, and red... Well, let's just pretend that it's an artifact so red doesn't start crying.
It's annoying to deal with, but it can be dealt with. Stuff like Nevermore and {Spell Crumple} being around encourages players to be smart about their deck building - you rely too much on one card, and don't prepare for what can happen to it, you're gonna have a bad time.