you can open it by taking the following steps:

- Collect shrimp and turn it into bait paste (shrimp + roundstone) (requires crafting technology level 3), then use it to bait the piranha fish away from the stone key (which takes 10 minutes); then, use a villager with master builder skills to move the stone key from the swamp to the crypt door

- Next, use a villager to open the crypt (requires master spirituality)

Note that you need to complete multiple puzzles prior to starting the "Tales from the Crypt" puzzle!