|Level 1||Level 2-3||Level 4||Level 5||Level 6-7||Level 8|
|Level 9||Level 10-12||Level 13||Level 14||Level 15-20|
- The Vault protects a proportion of your resources, such as Gold and Wood, from being stolen by your enemies.
- When your Headquarters is destroyed, the Vault protects the resources contained within it as well as an additional percentage of resources outside of it.
- Uncollected Resources within your Residences, Sawmill, Quarry, and Iron Mine can be stolen by attackers. The Vault protects the same percentage of uncollected Resources as Resources in storages.
- Note: VP and OP Rewards and Submarine treasures are completely safe. An attacker cannot steal anything at all from them. However, Resources can be stolen from your Resource Boat if one or more of your Resource Bases are taken over. See here for more information.
- The base amount that your Vault protects does count as storage space, and the Vault is the always the first storage that any Resources you get go to until it is full.
- Due to the fact that it is the only way to save your resources after losing on defense, it is probably the most important building, possibly even more than the HQ, and should be upgraded first or after resource producers if you cannot easily or reasonably afford it.
- Initially, the Vault is a door locked with a wooden bar leading underground, covered by wooden planks painted blue. It is reinforced by some sandbags on either side of it, as well as the rear side.
- At level 2, the roof of the Vault gains two additional wooden strips, with screws to hold them in place. The Vault is further reinforced with two more sandbags, one on each side of the Vault.
- At level 4, the roof changes to a corrugated iron material. Some sandbags are removed on each side.
- At level 5, the surroundings of the Vault are fortified with finer stone.
- At level 6, the wood structure is replaced with stone. The wooden door becomes a more solidified wood, with iron edges and a black iron bar.
- At level 8, the Vault gains two metal doors with individual handles. The roof becomes made of smooth iron.
- At level 9, the door changes to a spinning, watertight door.
- At level 10, the outer stone is reinforced with iron braces on the corners.
- At level 13, the Vault is now a spinning iron door on top of a stone platform. The door is also surrounded by smooth iron.
- At level 14, the Vault upper door plating underneath the valve becomes a tougher black iron.
- At level 15, the Vault door becomes a tougher black iron.
- The more you upgrade the Vault, the higher the base amount of resources are protected and the higher the percentage of resources outside of it that are protected.
- To see how much of what you have the Vault protects, click on the resource icons on the top right corner and see the amounts under "Protected by vault".
- The Vault is the only permanent building which has a description that changes every time you upgrade it. This is because the percentage of resources it protects is mentioned in the description.