The Lost Vault

01. The Event

The Lost Vault is not one event, it is three tabs in one window, and only the middle tab actually pays you. Daily tasks in Decipher Operations hand you Vault Keys. Keys open safes in The Lost Vault. Safes drop Commendation Medals. Medals buy stock in the Reward Exchange. Break any link in that chain and the whole event stalls.

Access

• ▸Chief's Office Lvl 6. Below that the event icon does not appear at all.
• ▸One icon, three tabs. All three surfaces sit inside the same window on the main screen.
• ▸Two seasons. The first run is anchored to your server's opening date; the second is anchored to your warzone's creation date.

The extra day

The Vault and Decipher Operations run 7 days. The Reward Exchange runs 8. That last day is spend-only: you cannot open another safe, but every medal you are still holding can still be turned into stock. Treat it as your dump day, not as a wasted day.

02. Vault Keys

Your entire run is decided before you open a single safe, because the free key supply is fixed at 1,080 keys — exactly 18 safes. Nothing on the board changes that number. Every decision in this guide is about what you spend those 18 opens on.

1,080 keys = 18 safes. 2,280 keys = 38 safes. A safe costs 60 keys; a paid refresh costs 90.

Which tasks pay keys

Only four of the six daily tasks pay keys, and two of those four are the hard ones. Skip the speedup task and the recruitment task every day and you lose 60 keys a day — 420 keys, or 7 of your 18 safes.

Front-load the speedup task. 1,000 minutes a day is nearly 17 hours of speedups. If you are hoarding speedups for a build push, spend them during this event instead — the same speedups pay you 30 keys and 100 points a day on top of the build.

03. The Safe Board

Every safe costs 60 Vault Keys, regardless of its rarity. This one line is the whole event. The game charges you the same price for a Rare safe as for a Legendary one, and the Legendary pays roughly 7.6× the medals. Rarity selection is not a nice bonus, it is the only lever you have.

Safe	Appears	Cost	Avg medals	Medals per key
Rare Safe	67.50%	60	1.75	0.029
Epic Safe	24.00%	60	4.22	0.070
Legendary Safe	8.50%	60	13.40	0.223

Average medals per safe, computed from the published drop rates. Rare safes are the appearance default, not the value default.

How the board behaves

• ▸Nine safes per board. The mix is rolled fresh on every refresh, so a board with zero Legendaries is normal — it happens about 45% of the time.
• ▸Expect 0.77 Legendary safes per board. Nine slots at 8.50% each. Two on one board is a good board; three is rare.
• ▸Open All costs up to 540 keys. Nine slots at 60 keys each. That is half your free budget on one button press.
• ▸Refreshing with an unopened Legendary throws a warning. Read it. That prompt exists because throwing away a Legendary is the single most expensive misclick in the event.

04. Safe Drop Rates

The Legendary safe is not just better on average, it is better on every line. More medals, more Decipher Chests, more hero fragments, and a jackpot chance 6.7× the Rare safe's. There is no category where opening a Rare beats opening a Legendary, which is why the rarity rule has no exceptions.

Decipher Chests

Decipher Chests feed keys back into the loop, which is the only reason the drop matters. Each chest averages 2 keys. A Legendary safe drops 10 chests 9% of the time, so it returns about 1.8 keys — roughly a 3% rebate on its own 60-key price. It will not change your plan, but it does mean an 18-safe run is really closer to 18 and a half.

05. Refreshing

Refreshing past a bad board costs you nothing, and that is the single habit that decides your run. Three free refreshes a day over seven days gives you 22 boards in total, which surface roughly 17 Legendary safes against the 18 opens your keys can pay for. The two budgets are tuned to land almost exactly on top of each other, so every Rare safe you open early is a Legendary safe you cannot afford later.

The refresh rules

• ▸Three free refreshes per event day. They do not bank. A day you skip is three boards gone permanently, which is the real cost of missing a day.
• ▸Clearing all nine grants a bonus free refresh that does not consume one of the three. It is a trap on a free run: clearing nine costs 540 keys to earn a refresh you already get three of.
• ▸A paid refresh is 90 keys — more than a safe. It is a marginal play at best, and only ever after your three free refreshes are spent.
• ▸Open before you refresh. Refreshing discards every unopened safe on the board, Legendary included.
• ▸Leave the confirmation prompts on. The "don't remind me today" checkboxes turn off the exact warning that stops you throwing away a Legendary safe.

06. Decipher Operations

The point ladder is not a participation prize — it is genuinely tight. It needs 4,000 Decipher Points and the event only issues 4,900 in total, at 700 a day. That is 900 points of slack across the entire week. You can miss exactly one full day and still finish. Miss two and the top of the ladder is mathematically out of reach.

The ladder

Twenty rungs, 200 points apart, from 200 up to 4,000. The free track's real payload is 240 Vault Keys at rungs 1, 5, 10 and 15 — nearly a quarter of your total key income, and it arrives in four lumps of 60. Each one is exactly one safe.

Overflow rewards

Past 4,000 points, every further 500 points pays Diamonds ×100 plus a 1-Hr Universal Speedup. A perfect free run banks 4,900 points, which is one overflow reward with 400 points to spare — so a flawless week is worth exactly one extra bonus over a merely good one. There is no visible cap on how many you can stack.

The Decipher Manual

The Manual is a real-money purchase and its price is not published anywhere in the game data, so judge it on what it grants rather than on value-per-dollar. It does two things: unlocks the paid ladder track, and lets you claim every daily task twice. Combined, that takes you from 1,080 keys to 2,280 — 18 safes to 38.

• ▸Buying it grants nothing on its own. It only unlocks the claim buttons. You still have to press Claim on every rung and every doubled task, including the ones you already passed.
• ▸Buying late still works. Every milestone you already cleared becomes claimable the moment you buy, so there is no penalty for deciding on day 5.
• ▸Two claims per task per day is the hard cap. The doubled claim covers keys and Decipher Points; whether the speedups and resource chests also double is not confirmed.
• ▸Doubled points break the ladder wide open. 1,400 points a day clears all 20 rungs by day 3 and turns the rest of the week into overflow rewards.

07. Milestone Rewards

The milestone ladder counts safes opened, not medals earned, and this is the one place the Legendary-only rule costs you something. A free 18-safe run reaches only the first two rungs. The 20-safe rung, worth 30 medals, sits two opens past your budget.

The chest generation follows your season: the second season's ladder pays Gen 2 Hero Materials Chests where the first pays Gen 1.

08. The Reward Exchange

Spend every single medal before the event closes. The shop sells a 100K Resource Supply Chest for 1 medal with an effectively unlimited stock, while the event rules say leftover medals are reclaimed and converted to a 10K chest each. Clearing your balance by hand is worth 10× letting the event do it for you, and it takes about thirty seconds.

Older states in the second season also stock Advanced Bulletproof Fibers (2 medals, limit 50) and Electro Core (2 medals, limit 100), and swap the Gen 1 chest for Gen 2.

The three skins

These are the only permanent stat gains in the shop, which is what makes them the real prize. Everything else is consumable.

Spend order on a free run

With roughly 240 medals and no skin in reach, buy in this order. It clears the whole balance and takes every capped line first, because the caps are what run out.

• ▸25 × 1-Hr Universal Speedup (25 medals). An hour of speedup for one medal is the best rate in the shop by a wide margin.
• ▸5 × Hardened Steel (25 medals). Capped and cheap. Take it early.
• ▸10 × Legendary Universal Hero Fragment (100 medals). The last capped line worth taking in full.
• ▸Everything left into 100K Resource Supply Chests. One medal each, no cap, and 10× what the automatic conversion would give you.

Note: the Hardened Steel line is labelled "Remaining Today", but nothing in the client resets it on a daily boundary. Do not plan on buying five more tomorrow until you have seen it reset yourself. The 1-medal-to-10K-chest end-of-event conversion comes from the shop's own rules text and is not confirmed anywhere else — another reason to spend the balance yourself.

09. Common Mistakes