The Vault is a building that protects resources from enemy attacks. The Vault is a fixed building, meaning its location is set in the Turf from the start of the game and cannot be changed by the player.
Depending on the number of maximum resources protected, anything more can be looted by enemies when they attack the turf. It can only protect food, wood, stone and ore, unlocking gold protection at level 25.
When a player uses a Migration Scroll, the player can only migrate with the number of resources protected by their vault and the rest is lost. During migration, the gold is protected by vault (same amount as the other resources) even if not at level 25.
Upgrading the Vault will increase the number of resources protected by the vault. At Level 25, gold protection is unlocked.