Piggy Bank

Unlike most containers this one will not sit on the floor. It wants a flat surface item underneath, a table, a workbench, whatever is to hand, which is a mild annoyance the first time you try to drop one into a cave outpost. The three later personal vaults all place directly on the ground, so this is the only one carrying that requirement.

Everything inside is saved with your character rather than with the world, and the consequences run long. You can pick the bank up while it is full and it keeps what is in it. Anything stored survives your death. It travels with you into other worlds and onto other servers. Other players cannot see or take any of it, and several people can open the same placed bank while each sees only their own things, which is what makes it the standard vault on a server where stealing is allowed.

Vendors can reach coins sitting in personal storage, and a shop window shows that pool next to the cash you are carrying. There is no reason to walk around with your savings on you, and since stored coins are never dropped when you die, there is a good reason not to. The displayed figure does stop counting at an absurdly large total, so a very rich character will see the number freeze.

Every bank you own opens the same container. Buying a second does not expand your storage, it only adds another door into it. That is still worth doing, since leaving one at each of your outposts means never walking home to deposit something. The habit becomes pointless once you pick up a Money Trough or an Eye Bone, either of which opens the same contents anywhere, including a world where you have never placed one.

The Safe, Defender's Forge and Void Vault behave the same way, except that each keeps its own separate set of slots, so they genuinely add space rather than duplicating what you already have. They also nest inside one another. A safe fits in a bank, a bank fits in a safe, and stacking them lets you carry a silly amount of storage in a single inventory square.

The one hole in the design, and it is a wide one. Personal storage is tied to the character, so when a hardcore character dies the entire contents go with them and none of it can be recovered by anyone. On that mode this is not a vault, it is one more bag you lose, and stashing your best gear in it before a risky fight makes the loss worse rather than smaller.