You have only opened up a small area so far. Here is the biggest one I have found so far, it had 12 crypts. Most of my others had around 6. Once you get the wishbone you can find more buried in the swamp, but those are more annoying, you end up digging yourself into a puddle of water, and they don't have anywhere near as much as crypts.

https://steamcommunity.com/sharedfiles/filedetails/?id=2610539106

The Crypts tend to spawn in the "thicker" swamp biomes only. What I mean by that is that if the swamp is just a small one, hugging the edge of some other biome, it tends not to have Crypts. I think the Crypts only exist in the "deeper in" parts of the swamp, kind of like how Black Forest has only Fir trees at the fringes and doesn't have Pines until deeper in.

Generally speaking swamps are pretty cluttered with Crypts if they are large enough. The thin "bacon strip" zones are sparsely populated from my experience. You need a nice sized zone like Species posted to get a good population of crypts. That place you lovingly named "hell" looks like it may host upwards of about 10 if you are lucky.

Originally posted by Malistair:

That place you lovingly named "hell" looks like it may host upwards of about 10 if you are lucky.

I don't think that area will actually contain any, as it looks like it is pretty thin with water on either side and black forest at the top left and botton left, so probably it is already fully explored.

Originally posted by Malistair:

Generally speaking swamps are pretty cluttered with Crypts if they are large enough. The thin "bacon strip" zones are sparsely populated from my experience. You need a nice sized zone like Species posted to get a good population of crypts. That place you lovingly named "hell" looks like it may host upwards of about 10 if you are lucky.

Sadly 'Hell' is on the very edge of where the biome becomes black forest. So, what's revealed is the extent of the biome. I guess it'd be larger if it didn't have a big body of water running through the middle of it.