Originally posted by Rhapsody:

I don't know about crypt variants, but they did reduce density of crypts a long time ago (two years or something). If you used to play on an old world seed, you may have ran into swamps containing crypts as close to each other as is physically possible, 30-50m between each. The change made was semi-retroactive since it prevented spawning of new "extra" crypts even on those old seeds/worlds.

There was another adjustment after mistland as well. I dont know if it was directly on the density but the total amount of crypts in the world was reduced.