Boo Hiss
Broken in Elements world.
Yeah, it's pretty broken, even with the high cost.
I'd up both the ability and casting cost 1, in an attempt to make it a very awkward card to put into play and fuel.
Just 2 of these would effectively stop your opponent from being able to do anything besides use abilities of creatures and permanents already on the field, as well as being insta-kill combined with RT or Eternity.