Sunken Crypts become accessible after defeating the second boss in Valheim, The Elder. You use the Swamp Key it drops to unlock these dungeons. The Swamp Key has unlimited uses, so don’t worry about farming extras.
Crypts are found exclusively in the Swamp but not every Swamp will have a sunken crypt. However, you can find multiple crypts in a single swamp. In our world, there’s a Swamp with 6 crypts and they’re all right next to each other.
|Rune Stones||Bonemass Location|
Sunken Crypt Tips
Sunken Crypts are similar to Burial Chambers because you can proceed down the branching paths at your own pace. There are no doors in crypts but most passageways will be blocked by a Muddy Scrap Pile. These are the primary source of Iron in Valheim.
Since you’ll be mining through tons of Muddy Scrap Piles, it’s a good idea to build an outpost near the entrance of the dungeon where you can repair your tools and rest between runs. To give some perspective, one sunken crypt can easily chew through 4 Antler Pickaxes.
Make sure you don’t break open a Muddy Scrap Pile when you’re out of stamina, that’s an easy way to plant a gravestone.
Encounters are going to be pretty similar to those you faced in the Burial Chambers, but you will have to deal with being Wet and there’s a new risk of Poison. Watch out for groups of Draugr archers, you probably don’t want to tank too many volleys.
Be especially careful of blobs. They apply a pretty serious Poison (~3 damage depending on equipment) that lasts for over 15 seconds. Blobs are best fought at range as they can sometimes still use their poison cloud while being staggered.