Zombie Frenzy is a game mode in which your objective is to protect your base for as long as possible against waves of zombies trying to destroy your base. The Zombie Frenzy can be played once every day and does not replace the already existing Zombie Defense.
Rewards include resources and up to two Common crates - depending on how many waves you manage to survive. Most players will only reach the first crate, while some may reach the second.
If you are confident that you will get quite far in your next Zombie Frenzy, make sure you have free slots at the Armory in order to receive your weapon crates.
The more waves you survive, the better the rewards!