Fortune Vaults

Fortune Vaults are a type of loot box containing mech skins, Credits and A-Coins. Fortune Vault Keys are required to open these. There are 3 varieties of Fortune Vaults, distinguished by the number of keys required to open them: 5-keys, 10-keys and 20-keys Fortune Vaults. You can click on the (i) button to see the possible rewards of each Fortune Vault and again click on the (i) button to see the probability of each reward. Each fortune vault starts with a population of possible skins (rare, epic and legendary skins for the mechs you unlocked through Gear Hub or through shop purchases), grouped into categories that share a set % chance (There is a category that comingles both rare and epic skins. It is designated here as "basic rare/epic skins" category to be distinguished from the rare skins category and the epic skins category). As you obtain skins from each category, the chance of obtaining the remaining skins in that category increases (the overall chance of that category remains the same while the skin count decreases). It is important to note that obtaining some of the skins within a category does **not** change the overall chance of any category, including Credits or A-Coins. Only after you deplete all skins within a category the probability of the remaining categories increases. It is theoretically possible to obtain all skins and remain with Fortune Vault rewards that include only Credits and A-Coins. However, there are hundreds of skins to obtain and the speed in which you can acquire skins will compete against the rate at which new skins are added to the game.

The following table shows the reward probability totals per category. The chance of each individual skin is equal to the total category chance divided by the category's total chance. So for instance, if your "Epic skin" category has 434 skins, each skin in the 10-key vault would have a chance of 10%/434=0.02%. After you've obtained 100 of them, the remaining epic skins would have a chance of 10%/334=0.03%. If you've already depleted the rare skins category the chance would then be 14.29%/334=0.04%.

As you can see, the 10-key vault generally offers the best expected value for each key used. 5-key vaults are sometimes useful when players are in need of credits but most of the time credits are plentiful while A-Coins are the resource bottleneck. The 20-key vaults are mostly used as a source of legendary skins.

## Maximizing A-Coins from Fortune Vaults

As analyzed in this database:

* It is never optimal to open the 5-key vault.

> The 5-key vault would take on average 16.7 keys per rare skin to deplete the rare skin category, while the 10-key vault would have done it in 33.3 keys per skin. Giving up the expected value of 3.72 A-Coins per each of those initial 16.7 keys just to gain an incremental 1.59 A-Coins for the next 16.6 keys would almost certainly end up being a net loss.
>
>

* Until you deplete all of the rare and epic skins, the 10-key vault provides the highest A-Coin rewards per key. Even when only legendary skins remain, the 10-key vault still provides more A-Coins than the 20-key vault. If you then try to deplete the legendary skins it would take on average 80 keys per legendary skin to break even (to make up for the lesser rewards you obtain while opening the sub-optimal 20-key vault)