The Vault Defence mode is reminiscent of the tower defence genre as your objective is to protect the vault which contains a flag from incoming hordes of zombies, although the zombies only have their eyes on the vault this time instead of eating your brains. However, despite you not being targeted by zombies; you will gain money for every zombie you kill which can then be invested in upgrading your defences by purchasing turrets, although you can also exchange weapons for turrets in order to strengthen your defences in the appropriate areas.
There are a wide range of new perks and chat commands included all guns are able to be equipped to turret defences for a limited duration in the Vault Defence game mode. Abilities including all turrets being immediately reloaded, upgraded with better weaponry, being provided with just enough money to buy a new turret, selling a turret for a much higher price and raising or lowering hexes to provide cover for your vault.