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Guide > Sandbox > Valheim

Valheim Bonemass boss guide: Location, how to summon and defeat

A guide to defeating Bonemass, including location, how to summon and gear required for arguably the most difficult Valheim boss.
After you've defeated the first boss, Eikthyr, and managed to get past the Elder boss in Valheim, you might run into a bit of a roadblock. This roadblock is called Bonemass, which is arguably the toughest boss in Valheim right now, despite being third on the list of five known bosses. In this guide, we will tell you how to find the location of Bonemass, summon this daunting boss, and defeat it.

Valheim Bonemass boss: Location & how to summon

Bonemass is a boss located in the Swamp biome, where players have also been spotting Odin from a distance. 

After you've defeated the Elder boss in Valheim (our full guide will help) it will drop a key to the Sunken Crypts, a very important item which will help you find the location of Bonemass.

valheim boss guide how to defeat summon bonemass location(Picture: Iron Gate)

In the Swamp biome, players will find the Sunken Crypts dungeon. Since the land is procedurally generated, you have to look around for it a bit.

Once you've located the Sunken Crypts, use your key found by defeating the Elder boss and head inside. Here, you will find a Runestone which will, after interacting with it, mark the location of the Bonemass summoning altar on your map.

valheim boss guide how to defeat summon bonemass location(Picture: Iron Gate)

To summon the Bonemass boss, you will need to find 10 Withered Bones. Thankfully, these are also located in the Sunken Crypts, so search the dungeon until you find 10.

With the 10 Withered Bones in hand, all you need to do is head to the Bonemass summoning altar (it is a giant skull) and burn the bones.


How to defeat Bonemass in Valheim

Bonemass is considered the most difficult boss in Valheim. He has three attacks you need to watch out for. First up, he's got a melee hit that can crush you instantly. Then, he also has a toxic AOE attack which filled the air, dealing a tonne of poison damage.

Lastly, he can summon Blobs, Oozers and Skeletons to fight beside him. To defeat Bonemass, you will need to dodge his attacks while clearing his summons whenever you can as to note get overwhelmed. 

valheim boss guide how to defeat summon bonemass location(Picture: Iron Gate)

You will need some mid-game gear to defeat Bonemass as well. We suggest you acquire the following equipment before trying to take him on.

  • Iron Helmet
  • Iron Scale Mail
  • Iron Greaves
  • Troll cape
  • Stagbreaker 

On the gear required front, you will need a good mace/club. Stagbreaker might be your best bet at this point in the game, and we've got a full guide on how to craft this seriously powerful early-game weapon. Alternatively, you can use an Iron Mace.

The reason for using Stagbreaker is simple. Bonemass is highly resistant to nearly all forms of damage, except for blunt attacks. He also heals during the fight if left unattended, so going for a constant melee onslaught is your best bet.

valheim boss guide how to defeat summon bonemass location(Picture: Iron Gate)

You should also stock up on some meads to use during the fight, and our full guide on meads has you covered in this regard. Be sure to Poison Resistance Mead to negate some of his toxic attack's damage. 

We recommend building a base where you can respawn close to the Elder boss' location in Valheim.

YouTuber Firespark81 shows you how to kill Bonemass using an alternative ranged tactic, which is a bit cheesy if you ask us.

With this guide, you should be able to find, summon and defeat Bonemass. Keep in mind this is considered the most difficult boss in Valheim right now, so don't worry too much if you die several times.

Once defeated, Bonemass will drop a Sacrificial Stone, which grants you greater resistance to physical damage. The daunting boss will also drop the Wishbone item (equipped in belt armour slot) which will lead you to hidden treasures in Valheim.