Bonemass is the third boss in Valheim. It’s a huge blob-like pile of bones and other animated grossness. You will fight Bonemass in the Swamp and will need withered bones that you find in Sunken Crypts to summon it. Bonemass is tricky because it takes very little damage and requires you to get in its face, but Bonemass does have a major tactical weakness — it’s very slow.

You will summon Bonemass at the giant skull summoning altar in the swamp. It’s filled with bubbling green liquid that will disintegrate the withered bones you offer to it. You should have plenty of withered bones by the time you fight Bonemass because you need to conquer lots of sunken crypts to get enough iron to make the recommended equipment.

You must defeat Bonemass to find Silver in the Mountains.


Bonemass is a meaty boss that is resistant to lots of damage types. Even if you normally don’t wield clubs, you should bring an iron mace into this boss fight. Bonemass will take more damage from an unskilled club than your skilled weapon.

Bonemass deals most of its damage with poison. You must bring Poison Resistance Mead to survive and you should also break out your best food for the occasion. We recommend having over 100 health for this fight.

Trophy10 Withered Bone (required for summoning)
WeaponsIron Mace (required for blunt damgage),
Banded Shield
ArmorIron Armor
FoodCooked Fish,
Cooked Meat,
PotionsPoison Resistance Mead (required),
Medium Stamina Mead,
Medium Healing Mead

Bonemass Strategy


Bonemass has three attacks. A basic attack and two special attacks:

  • Basic Attack
  • Toxic Cloud
  • Blob Bomb

Basic Attack

Bonemass takes a swipe at the target inflicting high damage and high knockback. The attack is strong enough to throw the target completely out of melee range.

Toxic Cloud

Bonemass prepares to spew a toxic cloud from its mouth, then sprays it side-to-side. The cloud will spread out to its maximum size after a few moments and then linger for a few seconds.

If you get poisoned, just unload on Bonemass until it changes aggro. Though you want to try and avoid getting poisoned in the first place.

Blob Bomb

Bonemass pulls a chunk of itself from underneath its arm. Bonemass then winds up and throws the green slop towards the target. The blob bomb is quite inaccurate and often misses the player, but that doesn’t matter at all. The blob bomb will spawn 1-3 blobs where it impacts.

Don’t let these blobs stack up. You don’t want to get swarmed in the middle of your fight. Bash them to death as soon as they become a problem.

How to Kill Bonemass

Bonemass has a fatal weakness, Bonemass moves and turns very slowly.

We can use this to defeat the boss with relative ease. The best strategy needs two people and you’ll want to pull in a friend to give you a hand. Ideally, you will be in voice chat where you can easily communicate with your teammate.

You want to alert your team whenever you notice Bonemass preparing to release the toxic cloud. You also want to alert your team whenever Bonemass is switching targets.

You will also want to prepare the battlefield a little bit.

Flatten the area around the skull altar or another large object that can be used as cover. You will kite Bonemass around this and hide behind it when Bonemass releases the toxic cloud — the cover should be nice and thicc.

Now that everything is prepared, it’s time to summon Bonemass.

You will attack Bonemass from opposite sides. Whichever player Bonemass is facing should kite it around without attacking. Once Bonemass loses aggro, it will turn around to face the other player.

At this point, the roles reverse and the player who was just kiting Bonemass will start bashing it with their mace. The other player now must kite Bonemass around — stay close enough to keep its attention with melee attacks, but try not to get hit.

Repeat this process until Bonemass is defeated. You should find it fairly straightforward because of all your preparation — not necessarily easy, though.

Updated on November 1, 2021

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