2 reasons why this fails. 1. You cant just disable the damage of a zombie class. 2. You cant give "Negative" side effects to upgrades you can't sell. That would be unhandy. That's the downside of this upgrade, if you disable the damages for a class and give nothing bad in return then you just won the game. So it needs something that balances it a bit. Ok, let's say, Howlers do reduced damage (50%), because they are actually too strong. okay remove that howler and pick up a new zombie who can shoot guttling hooks +1, no wait, +459 ! I'm Hundred2 and this is my favorite idea on the forums. delete howler and let it be... its useless howler are not used and its just fuckin annoying.