Bonemass
Boss 3 of 8, fought in the Swamp. 5,000 health across the whole fight.
How to summon
Withered BonePlace Withered Bone on the altar in the Swamp. The altar is marked on the map once you find it, and the offering is consumed, so bring a spare set if you plan to fight more than once.
Best weapons
Damage per hit at max quality, after Bonemass's own resistances are applied. One entry per weapon skill, so this is a choice of weapon TYPE rather than eight variations on the same mace.
| Item | Effective | Breakdown |
|---|---|---|
 Butcher Knife | 1,000 | True 1,000 |
 Frostfire Sledge | 496 | Fire 5, Blunt 345, Frost 146 |
 Lightning Strike | 360 | Lightning 360 |
 Frostfire Knucklechains | 283 | Fire 5, Blunt 120, Frost 146, Slash 12 |
 Frostfire Greatsword | 259 | Fire 5, Frost 146, Slash 108 |
 Frostfire Greataxe | 243 | Fire 5, Frost 146, Slash 92 |
 Frostfire Crossbow | 215 | Fire 5, Frost 146, Pierce 64 |
 Frostfire Bow | 199 | Fire 5, Frost 146, Pierce 23, Spirit 25 |
Figures are per hit at maximum quality, before skill level, backstab and the boss's armour. They rank weapons against each other rather than predicting a time to kill.
Drops
| Item | Amount | Chance |
|---|---|---|
 Bonemass Trophy | 1 | 100% |
 Wishbone | 1 | 100% |
Bonemass
The mass takes the brunt of your blows. The effort required to raise your shield lessens, and you can withstand harder hits.
- Block stamina -100%
- Blunt, Slash, Pierce: Slightly resistant
- Block stamina -5
Hang the trophy on a sacrificial stone to claim the power. It lasts 300 seconds and can be used again every 20 minutes.
After Bonemass dies
The world escalates. These start appearing once the kill is registered:
Progression Order
What the game says about Bonemass
At the altar
Wanderer, look to your feet That tread upon our tomb One thousand bones without their meat Will drag you to your doom
The dream before
You dream of a hundred ghosts crowding thickly around your bedside, seeking warmth and life until something thumps deep below the ground and they jump like crumbs on a drumskin and are gone.
Its last words
Thank you, warrior. We who lived on in this shape were denied the peace of death for too long. We go now...
Bonemass is boss 3 of 8, fought in the Swamp with 5,000 health. It takes extra damage from Blunt, Frost, which is what decides the weapon rather than raw damage numbers — the best option against its resistances is Butcher Knife at 1,000 per hit at max quality. Summon it with Withered Bone, and expect the world to change afterwards: Skeleton start appearing once the kill registers.
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How to beat Bonemass
What is Bonemass weak to in Valheim?
Blunt, Frost. It ignores Chop, Poison, Pickaxe entirely, so a weapon that looks strong on paper can do nothing here. The weapon table above applies those resistances rather than listing raw damage.
How do you summon Bonemass?
Place Withered Bone on its altar in the Swamp. The offering is consumed on use.
How much health does Bonemass have?
5,000 across the whole fight. There is no damage cap or enrage timer, so the practical limit is how long you can keep landing hits — which is why the weapon that beats its resistances matters more than the one with the biggest number.
What does the Bonemass power do?
Bonemass is what Bonemass grants at a sacrificial stone once you carry its trophy. It runs for 300 seconds and then needs 20 minutes before it can be used again, and only one Forsaken power can be active at a time — so it is chosen for the fight ahead rather than kept on permanently.
What changes in the world after you beat Bonemass?
New creatures begin to appear: Skeleton. Beating a boss sets a world key, and several spawn tables are waiting on exactly that key — which is why a biome you thought you had cleared starts producing things you have never seen. The change is permanent and applies to the whole world, not just your character.