Bonemass is a different kind of fight from the bosses before him. He resists most damage types, poisons everything around him and calls in helpers. Blunt damage works best against him, so bring a mace or a sledge. This guide shows where to look for his runestone in the Swamp, how to gather ten Withered Bones, what keeps you alive through the poison and what the Wishbone he drops is for. It covers Valheim 1.0 with patch 1.0.20 (15 October 2026), with the Forsaken Power described from the official Call to Arms list.
The Swamp and the Sunken Crypts
Bonemass is the boss of the Swamp, which you head into after beating The Elder. The key point: without the Swamp Key you can’t enter the Sunken Crypts, and that’s where everything you need for Bonemass is: the runestone with his altar location, the Withered Bones to summon him and the Scrap Iron you smelt into iron.
The Swamp is the iron biome. With the Scrap Iron from the Muddy Scrap Piles inside the crypts you craft iron tools and weapons. You’ll also gather Entrails, Ooze, Guck, Bloodbag, Chain, Ancient Bark, Root and Turnip Seeds here. Root drops from Abominations and goes into Root armour.
The Bog Witch, the game’s third trader, also lives in the Swamp. From her hut she sells ingredients for feasts and new meads. How the Swamp fits into the wider journey is covered in our biome order guide.
How to summon Bonemass: ten Withered Bones
- Open your first Sunken Crypt with the Swamp Key.
- Find the runestone inside that shows the altar location.
- Collect ten Withered Bones. They’re in the Sunken Crypts and in Muddy Scrap Piles.
- Brew a poison resistance mead, grab a blunt weapon and offer the bones at the altar.
The ten bones don’t have to come from a single crypt. Collect them as you go, since you’ll be visiting crypts for iron anyway.
Why a mace or a sledge
Bonemass resists most damage types. Blunt damage works best against him, which means maces and sledges. Good examples are the Stagbreaker or the Iron Mace.
The Iron Mace is also a reason to clear a few crypts and collect iron first. Your gear matches the biome, and in the Swamp that’s iron. Where the whole line goes, from stone all the way to Nord, is covered in our gear progression guide.
Attacks: poison, blobs and skeletons
| Attack | What it does | How to defend |
|---|---|---|
| Melee strike | A heavy hit when you stand next to him. | Keep your shield up and strike between his hits. |
| Poison cloud | Poisons the area around him. | Poison Resistance Mead. |
| Summons | Blobs and skeletons appear around the boss. | Deal with the helpers before they surround you. |
You’ll run into poison often in the Swamp, and even more at Bonemass, so the Poison Resistance Mead is mandatory kit. Since The Bog Witch patch (29 October 2024) mead bases are made in the Mead Ketill rather than the cauldron. What else to cook so you don’t go in short on health is covered in our food guide.
The fight goes better in a group. One player keeps Bonemass busy, others hit him with blunt weapons and someone watches the blobs and skeletons.
Reward: the Wishbone and the Forsaken Power
Bonemass drops the Wishbone and his trophy. The Wishbone finds silver and buried treasure: it starts to buzz when you’re above a deposit. Silver in the mountains is found exactly this way.
Hang the trophy on the Sacrificial Stones at the spawn. You activate the Forsaken Power with a key and it lasts 300 seconds. According to the official Call to Arms list (9 September 2025) it gives:
- 25% resistance to pierce, slash and blunt damage,
- 100% less stamina used for blocking,
- +5 stamina back per block.
It’s a defensive power for hard fights: blocking costs you nothing and even gives stamina back. Older guides describe a different version, which no longer applies after Call to Arms.
What Bonemass unlocks
With the Wishbone and an iron pickaxe you head for the mountains. Silver in the Mountains is tracked down with the Wishbone and mined with an iron pickaxe. The cold up there hurts, though, so you won’t last without protection. How to prepare for the mountains and summon their boss is covered in our Moder guide. If you still need the Swamp Key, go back to The Elder.
Join our Discord to find out who’s free for a crypt run, or to get advice on your Bonemass loadout: Discord GamersTogether.
FAQ
Ten. You collect them in the Sunken Crypts and Muddy Scrap Piles in the Swamp, and you get into the crypts with the Swamp Key from The Elder.
A blunt one, such as a mace or a sledge, for example the Stagbreaker or the Iron Mace. He resists most other damage types.
Brew a Poison Resistance Mead. Since The Bog Witch patch, the mead base is prepared in the Mead Ketill.
It finds silver and buried treasure and buzzes above a deposit. In the mountains it leads you to silver, which you then mine with an iron pickaxe.
Information verified on 19 October 2026. More guides are waiting in the Valheim hub.