From Dragon Mania Legends (DML) Wiki
“A perfect place to store many of your dragons at once.”
The Dragon Vault has a size of 6x6 squares and can be purchased in exchange for 25,000,000 Gold. It is built instantly and yields no experience upon completion. Once purchased, it can not be sold. However, as long as there are no Dragons inside this building, it can be stored inside the Inventory by selecting the Vault and then tapping the button.
Storing Dragons inside the Vault is done by selecting the building and then the option. From here, selecting any free slot by pressing the Select button will bring up the snapshots of all the housed Dragons the Trainer currently has. Selecting any of the snapshots will automatically store that Dragon. The Dragons can be filtered by their Element, by All, or species name using the button. Dragons that are currently busy (such as those that are breeding, exploring ruins, having their Elements awoken, skill-training in the Dragon Academy, or undergoing a process in the Fountain of Youth) may not be stored until they are available. Additionally, Boss Dragons are prohibited from being stored inside the Dragon Vault.
Storing Dragons can also be done by selecting a Dragon in their Habitat, opening their Codex Entry, and then pressing the Vault button, which will automatically assign the Dragon to the first free slot in the Dragon Vault. Rehousing Dragons from the Vault can be done by accessing the building, pressing the Place button, and then choosing a free Habitat spot.
Inside the Dragon Vault, the Trainer can see the snapshot of the stored Dragons which displays their image, level, Enchantment Level, given name, rarity, Elements, and the i button. Pressing this button will bring up the Dragon's base Codex Entry.
Dragons stored inside the Vault become semi-inactive, as they will not generate Gold or actively participate in any other feature of the game. However, where applicable, they will count when calculating the strength of opposing Dragons in any battle venue. Additionally, stored Dragons can be hired by friends of the Trainer, they can be ascended, and they will also count towards quests or tasks that require the Trainer to have a minimum number of Dragons to complete said objective.
The Dragon Vault can have up to one hundred slots. The first slot of the Dragon Vault is offered for free while subsequent slots have to be bought in exchange for Gold. The next nine slots cost 5,000, 10,000, 50,000, 100,000, 500,000, 1,000,000, 5,000,000, 10,000,000, and 50,000,000, respectively. After purchasing the tenth slot, each subsequent slot will have a price of 100,000,000 Gold. The total amount of purchasing all slots is 9,066,665,000 . Purchasing slots is done individually by heading towards the slot that contains the "GET A NEW SLOT" text and then tapping the green button underneath it. No confirmation window will pop up and the slot will be acquired on the spot.
The number of Dragons currently stored in the Vault and the current capacity of the Vault are shown at the bottom of the Vault separated by a slash.
The Dragon Vault can be moved to a different location by pressing down on the building and then dragging it to the new location or by pressing down on the building and then simply tapping the desired location. The Dragon Vault is selected for moving when the X and buttons appear underneath it. An arrow will appear on each side of the Dragon Vault indicating if it can be placed in the new location or not. If the arrows are gray, the spot is not accessible, and if the arrows are green, the Dragon Vault can be placed onto that spot. The repositioning is confirmed through the button while pressing the X will cancel the moving and restore the default position of the Dragon Vault.