Vault of Villains is a mini-expansion of 64 cards. It requires Boss Monster 1, 2 or 3 to play. It is fully compatible with all Boss Monster sets.

It's a miniboss mini-expansion! Vault of Villains allows you to power up your rooms with minibosses, payable and promotable minions that make rooms stronger and stronger! Includes 15 minibosses (enough for any Boss Monster base game) and enough coin generating rooms to keep them paid! Also includes five new bosses and 8 new spell cards.