In the Vault building you can deposit gold to get it back later with interest.
The Vault is one of the special buildings that needs to be unlocked before you can use it. You can unlock the Vault by purchasing any pack. Upgrading the Vault also requires an extra pack (minimum USD amount specified) for each level.
When opening the Vault you can select a Certificate of Deposit which specifies the deposit term. The interest and maximum amount you can invest depend on the vault level. Once you deposit an amount, you can collect it with interest after the term expires.
There are three (four for Vault level 5 and 6) possible terms, 1 Day Deposits, 3 Day Deposits and 7 Day Deposits (and 14 Day Deposits for Vault level 5 and 6).
The base interest is 1% for the 1 Day Deposit, 10% for the 3 Day Deposit, 15% for the 7 Day Deposit.
Each Vault level has its boosts to increase the Bonus Interest Rate and the Maximum Deposit Amount.
There are various ways to increase the Vault Maximum Deposit Size and Bonus Interest Rate.
The Bonus Interest Rate can be increased via the Vault Deposit Size and Interest Rate research project in the Building Development research category (7%) and via the Vault Insignia (6%).
The Maximum Deposit can be increased via the Vault Deposit Size and Interest Rate research project in the Building Development research category (5,000), via the Vault Insignia (9,600), and via the VIP levels (including Daily Bonus Club bonus) (1,500).
In below table we have made an analysis of what the best deposit is for each Vault level based on the amount of gold it returns per day.
|Vault Level||Term [days]||Max Deposit||Interest [%]||Gold per Day|
Disclaimer: the maxima and percentages are based on a VIP Vault maximum bonus of 1000 (the higher level VIP, without Daily Bonus Club), and no research from the Building Development category and no Insignia. Having any of all of these active will mean higher Deposits and/or interest rates for all terms, which will favor the shorter terms (more benefit per day).
Note that for Vault levels 5 and 6 I have not been able to include the analysis of the 14 day deposit since I don't know the base max amount and the base interest.
The numbers in bold are giving the most gold per day return for each vault level. This is for vault levels 1-5 the deposit with the 1 day term and for vault lvl 6 the 7 day deposit.
This is no get quick rich scheme, even getting 1634 gold per day is almost nothing compared to the huge requirements. Vault upgrades should for sure not be a reason to buy packs, but if you buy packs anyway, you might deposit the gold in the vault to get a little bit extra.