How Do I Use The Cheaters 20 To Defend?

The cheater's dice can only be used for defense while you are being attacked or if one or more of your buildings has been destroyed. To use it, tap on the shield with the red die in the upper right corner of the screen. If you are not being attacked, it will tell you so. Otherwise, it will tell you to tap on the screen to use the cheater's die. Tap on the screen, but NOT on a shield - tapping on a shield will just defend the single building as usual. Tapping anywhere else should give a little flash and all of the shields should disappear, along with any invaders. Any buildings that have been destroyed should be rebuilt (although I haven't tested this feature myself). Basically, it's just a way to clear all the attacks at once. Not really worth it IMO, but you need to do it once to clear the quest.

Many people have said that they have used the dice for defense, but it didn't clear the quest. I tried a few times before I realized that I shouldn't be tapping on a shield and then it worked fine.