Impossible to get the last deposit box key (with the sanctum key)

[Cdent]

Hi,
I think I tried everything :
Lost and found, root cellar, dead-ends, trading post, ...
I have already found 3 deposit box keys but I cannot find the last one (related to a sanctum key)
I am already at day 156, I'm starting to lose hope

Does anyone have any tips for this key ?

[Lactose Intolerant Volcano God]

I'm having a similar experience, so I don't have an answer, sorry. :-(
But these are places where I have found the other Vault keys:
in digs spots, Attic, Conference Room, Sauna, Walk-In Closet, and Wine Cellar.
So I've been mainly trying those plus the Trading Post.
I hope we find the key soon!

[ioan]

It can also spawn in the Music Room. Also you might check special key from the Locksmith, but I'm not sure about it.

[Silyon]

The Vault Box key is a "Major Key", though the specific box it goes to is random. Thus it can appear in any location a Major Key can. Music Room and Locksmith both have guaranteed ones, and they can sometimes show up in trunks, dirt piles, and bedrooms. You want high "item Find" luck to spawn more items across the estate and empty the item pool. Luck is a stat the game tracks and can be manipulated with rooms like Veranda, Maid's Chamber, one of the upgraded Cloisters, as well as the Rabbit Foot item.

[bexler774]

It sounds like you have the right ideas, along with others who have replied. Ultimately though, the RNG is what will determine your success here. This is one of the last things I ever did in the game, and long after I'd found every other sanctum key. Not my favorite part of the game by any stretch.

[Mizerakl]

Have the same issue, but I think my problem is related to save file. I opened it once, finished the run, but did alt + f4 on "save & continue" screen and after that never found it again.

[Essaria]

I had a similar issue and ultimately got it by spawning all other major keys in a single run, then drafting the music room so it was the only key legal to spawn