Searched can't find

[Masque]

New to the game. Can't find any info on what these gemstone-named keys are. Ruby, Sapphire, etc.

Anyone can put me some knowledge?

[Fel]

If you are in the castle they unlock access to rooms with mini-bosses and you need to defeat all but one to get access to the door to the next area.
(they are colored keys, not sure what their name is so it might not be them)

[gbors]

Just search for "ruby key dead cells" on google, and select the result from deadcells.fandom.com . There's hardly anything that's not found quickly on the fandom wiki.

The keys are parts of a matching trio, and are used to unlock an outfit.

[Redlegoguy1]

There is a lectern with a book on it in the spawn room that gives hints on crossover items. It is right before the door where you start a run. Interacting with it will give you hints on how to unlock the various crossover outfits, and the gemstone keys are part of the slay the spire crossover outfit. If you don't want to spoil it, I suggest reading the book hint for how to complete the set.

Originally posted by gbors:

Just search for "ruby key dead cells" on google, and select the result from deadcells.fandom.com . There's hardly anything that's not found quickly on the fandom wiki.

The keys are parts of a matching trio, and are used to unlock an outfit.

Also, an important note on this, https://deadcells.wiki.gg is the official wiki now. There have only been two major updates since that change, so a lot of the fandom wiki info is still accurate, but it's quickly becoming outdated. There's no pages for most of the 3.3 content, and 3.4 doesn't even have its patch notes in yet. The new wiki already has a significant amount of that info, and that gap is likely only going to widen, so do try the new one when you need it.

[Masque]

I looked it up on the wiki -- thanks all.