I can't get this room to appear. late game spoilers

[Bro&]

So I'm quite late in and for my next move I need to make it to |the vault , but I've run the past 8 or so runs focusing on blue rooms specifically but it hasn't appeared even through multiple re-rolls and configurations.

is there a particular condition for it to spawn? Like does it require a certain kind of door or adjacent room? I've only drafted it like 9 times.

[ItsDarthChaos]

As far as I know I don't think there are any special conditions for it. It's just rare, and it costs 3 gems, so you have to make sure you plan on having plenty for when it pops up.

[Doombringer]

You can change it's rarity, try getting it from library, or do schoolhouse and a bunch of drafting rooms to gets tons and tons of re-rolls (but you will need a lot of gems for this).

Alternatively, the 12-star constellation makes all dead-end rooms show up reliably.
(also shows up at 22, 27, 32, 37, 42, 45, 47 stars)

[Bro&]

I eventually found it, it drafted next to a gift shop which may or may not be relevant at all. I wasn't drafting any shops until that run so it might be significant

[(Edgy) Asriel Dreemurr]

It might just be that it’s weighted to appear more often in higher ranks, due to the higher gem cost, on top of just being rare to begin with.