The Swamp Key is one of the mid to late-game boss items that you can acquire after defeating the second boss in Valheim, The Elder.
This key allows you to access the Sunken Crypts that you will need to farm iron scraps and other resources from.
To access the Sunken Crypts, at least one person should have a Swamp Key and must use it on the locked gate.
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Where To Get Swamp Key?
The Swamp Key is only obtainable by defeating The Elder, the second boss in Valheim, and this is the only way to get them in the game.
The Elder is relatively easy to fight, and defeating it will cause 2 Swamp Keys to be dropped, and soon after, you can continue to progress into the game.
Your only hope for efficiently farming Iron is to defeat The Elder and use the Swamp Keys to unlock Sunken Crypts where you will farm it.
For more info on how to defeat The Elder, check out our Valheim The Elder Boss Guide.
Swamp Key Use
The Swamp Key is used for gaining access to the Sunken Crypt, which is found in the Swamp biome, usually beyond the Black Forest.
You will see the entrance to a Sunken Crypt appearing as a stone structure with Green Torches on each side of it.
Gaining access to a Sunken Crypt is the start of your progression to Iron-tier items as you will mostly find Scrap Iron along with other resources related to the Swamp biome.
It is known that later on, you will be able to get Iron Scraps in the Swamp biome itself, but this is hard until you defeat the third boss, Bonemass.
How To Find Sunken Crypt?
Sunken Crypts can exist in almost any Swamp biome, but not all will have them, and this mainly depends on the size and your world’s map seed.
Sometimes you may find no Sunken Crypts in a smaller Swamp biome and will have to search for larger ones.
The bigger the Swamp biome that you are exploring, the better the chance you will come across more Sunken Crypts.
A large Swamp biome can sometimes have 2-4 Sunken Crypts spread amongst it, allowing players to farm enough Scrap Iron for their Iron armor and weapons along with upgrades.
It is necessary for you to gain access to the Sunken Crypts because without it, gaining Iron is slim, and you will have trouble progressing in the game.
Through the acquisition of Scrap Iron, you will be able to work on your Iron-tier equipment, allowing you to, later on, face Bonemass.
Without Iron-tier equipment, the chances of you dying in the Swamp and other more complex areas is very likely as Iron is a significant upgrade.