I completely agree Phazonfish. Not to mention they would just find other spells that would be as powerful. So, no point in trying to fight it. Forces me to simply allow an encounter to be defeated in this way. The whole point is to beat encounters, this is just another tool to beat encounters with. My biggest concern is they go to fight Tiamat and she's caged and game over.. Now what... But she would be an ancient dragon and too large. Just as an example though.