Bonemass is Valheim’s third boss and the first true difficulty wall — a giant, toxic blob lurking in the Swamp. Beat him and you unlock the Wishbone, your key to finding silver. This guide covers exactly how to prepare for and defeat Bonemass.
How to summon Bonemass
Place 10 Withered Bones on the sacrificial stones at his altar in the Swamp. Withered Bones drop from Sunken Crypts and muddy scrap piles, so you’ll gather plenty while mining iron.
Prepare before the fight
- Weapon: an upgraded Iron Mace. Bonemass is weak to blunt and fire but resistant to pierce, slash and poison — so a mace is far better than a sword here.
- Mead: bring plenty of Poison Resistance mead. His attacks and aura deal heavy poison, and without resistance they’ll shred you. See our mead guide.
- Food & armor: your best Swamp-tier food and upgraded iron or root armor.
The fight
Bonemass is slow, so this is a tank-and-spank. Stand in close, swing your mace, and keep your poison resistance mead topped up as it expires. He summons skeletons and blobs and unleashes a poison gas cloud — step out of the cloud, clear adds if they pile up, and heal with mead and food between hits. Fire arrows also chip him down if you want a ranged option.
Rewards
Bonemass drops his trophy and the Wishbone, which pings near buried treasure and silver veins — essential for the Mountains. Mount his trophy for a Forsaken Power that boosts physical damage resistance. Full details on the boss tracker.
Take him on together
Bonemass is much easier with a partner trading hits. A Valheim dedicated server keeps your world online 24/7 so your crew can gear up and fight him together. See the full boss order guide.
Frequently asked questions
What is Bonemass weak to?
Blunt and fire damage. Use an upgraded Iron Mace; avoid pierce and slash, which he resists.
How do you summon Bonemass?
Place 10 Withered Bones at his Swamp altar.
What does Bonemass drop?
His trophy and the Wishbone, which finds buried treasure and silver.
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