The Mausoleum is a Functional Item that allows you to store 9 zombies. Because you can only have 16 zombies on your farm at the same time, a Mausoleum is useful because it allows you to choose which zombies you want to take on your Invasion. Zombies that are inside the Mausoleum still grow hungry at the same rate as those on the farm.
The Mausoleum 2 is a upgrade to the Mausoleum, giving 3 more storage slots for your zombies, so you can store 12 in total. You may upgrade to the Mausoleum 2 even with a locked Mausoleum, but you still must obtain the Rusty Fragments to unlock it.
Whether you have the key or not, you can purchase the Mausoleum 3, which adds 3 more storage spaces. This brings the total to 15, meaning you can store all but 1 Zombie in your Mausoleum. This third upgrade has flares on it, that glows green at night!
When pulling a zombie out of the mausoleum, if the zombie's picture to the right is darkened/black, clicking the -> arrow to take the zombie out will crash your game and force you to restart Zombie Farm in your Multitasking Menu. Version 0.85 solved this problem.
In Version 0.83, 0.84 zombies in the Mausoleum won't get hungry, even if they are swapped out of it. The way to make them hungry again is to use Insta-Hunger, or invade an enemy.
It might occur that in Version 0.85 you cannot swap zombies with the <--> button. Restarting the game can solve this issue.
If you put any zombie in mauloseum, you may get a chance for its stat to go to master and say the amount of invasions is 2,000 or higher. (Version 0.86)