I don't think it needs a timer but something needs doing about gravity pull.
Hmm... Yeah, this is a problem.
I think a timer is the best way to go though, since it does prevent you from perma-freezing something, but as is also completely prevent you from doing anything to any new creatures your opponent plays.
Should the timer be 4 or 5?
Maybe 5 unupped and 4 upped? Should I make their costs the same if I do that?