Opening the Mausoleum
To gain access to the mausoleum, the player must first purchase it. It can be found in the items section of the market under the heading "functional." When it is first on the farm, the mausoleum is locked. To unlock it, the player must obtain three rusty fragments as loot from invasions. These can be combined to form the rusty key that unlocks the mausoleum.
Storing Zombies
Once the mausoleum is open, it can be used to store extra zombies. A zombie can be stored in two ways. Find it on the farm. Select it. Hit the blue "i" button next to the zombie's name. You'll then get the option to sell the zombie or to put it in the mausoleum. You can also go to the "RIP" menu, find the zombie, and put it in the mausoleum from there.
Removing Zombies from Storage
To take a zombie out of storage and put it on the farm, first make sure you have less than 16 zombies already on the farm. Then you can go to the "RIP" menu and select mausoleum. Find the zombie and retrieve it. You can also simply find the mausoleum on the farm and select it that way by pressing the blue "i" button next to the mausoleum name.
Upgrading the Mausoleum
When it is first unlocked, the mausoleum offers six extra slots to store zombies. However, it can be expanded to hold more zombies. The game offers several upgrades. Each one gives you an extra three slots. To upgrade the mausoleum, simply go to the items section of the market menu. The upgrades are found under the "functional" heading and can be purchased there with brains. Brains must be either obtained in the game through invasions or purchasing them using real money in the "Brains" section of the market.