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Bonemass Boss Guide — Valheim's Third Forsaken
Bonemass is the third Forsaken boss and the biggest skill check in Valheim. Found in the Swamp, this massive blob of bones and ooze deals heavy poison damage and summons minions. Many players hit a wall here — but with the right preparation (Iron Mace + Poison Resistance Mead), Bonemass becomes manageable. This guide covers his critical blunt weakness, all attack patterns, the best weapon choices, and the Forsaken power that makes you nearly unkillable.
3rd
Boss Order
Swamp
Biome
10
Withered Bones
🟡
Blunt Weakness
1. How to Summon Bonemass
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Location
Bonemass's altar is a massive green-glowing skull in the Swamp. Find it via red runestones in Sunken Crypts. The altar area is always wet and surrounded by deep water — use a Hoe to raise ground around the altar, creating a dry, flat arena. This is the single best preparation tip for this fight.
Summoning Requirements
| Item | Quantity | How to Get |
|---|---|---|
| Withered Bone | 10 | Drops from Muddy Scrap Piles in Sunken Crypts (requires Swamp Key from The Elder). Also drops from Skeletons in the Swamp. |
2. Stats & Weaknesses
| Attribute | Value |
|---|---|
| Health | 5,000 HP |
| Damage Type | Poison (AoE cloud), Blunt (melee swipe), Pierce (summoned minions) |
| Weak To | 🟡 Blunt damage — Iron Mace, Iron Sledge, Frostner (if obtained early) |
| Resistant To | Pierce (bows, spears), Slash (swords, axes) — all heavily reduced |
| Immune To | Spirit, Fire, Poison, Stagger |
3. Attack Patterns
| Attack | Description | How to Counter |
|---|---|---|
| Poison Cloud (AoE) | Rears back and vomits a massive poison cloud around itself. Heavy DoT, long duration. This is the attack that kills most players. | Drink Poison Resistance Mead before the fight. When he winds up, run away immediately. The cloud radius is large but avoidable at sprint distance. Poison Resist mead reduces damage by 75%. |
| Melee Swipe | Close-range arm swipe dealing blunt damage. Telegraphed by Bonemass winding one arm back. | Roll backward or block with an Iron Buckler/Banded Shield. Parry if confident — he's parryable. |
| Minion Throw | Pulls a Blob or Skeleton from his body and throws it into the arena. Adds build up over time. | Use the Iron Sledge (AoE) to clear minions quickly while still damaging Bonemass. Or kite minions away and kill them separately. |
4. Best Weapons & Strategy
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Recommended Weapons
| Weapon | Why |
|---|---|
| Iron Mace ⭐ | Best weapon for this fight. Blunt damage exploits Bonemass's primary weakness. Upgraded to Level 3-4 for maximum damage. The Iron Mace is the community consensus #1 pick. |
| Iron Sledge | Excellent secondary. AoE blunt damage clears Blobs and Skeletons while also hitting Bonemass. Cannot be used with a shield though. |
| Frostner | If you're willing to brave the Mountains before Bonemass, Frostner's frost slow effect + blunt damage makes this fight significantly easier. Silver-tier weapon. |
Strategy
- Flatten the arena with a Hoe: The swamp around the altar is wet and uneven. Use the Hoe's "Level Ground" function with a Workbench nearby to create a dry, flat fighting arena. This prevents the constant Wet debuff and gives you room to dodge.
- Poison Resistance Mead is MANDATORY: Drink before the fight. Each bottle lasts 10 minutes. Bring 3 bottles. Without poison resistance, the poison cloud kills you in seconds.
- Use a shield and learn his rhythm: Bonemass attacks slowly and predictably. Block/parry his swipe, hit him 2-3 times with the Iron Mace, then step back. Repeat.
- Clear adds immediately: Blobs and Skeletons pile up. Switch to the Iron Sledge or quickly Mace them down before they overwhelm you.
- Don't use a bow: Pierce damage is heavily resisted. A bow will take forever to kill him. If you must use ranged, Frost Arrows can slow him.
- Watch your stamina: The constant Wet debuff from the Swamp slows stamina regen. Bring Tasty Mead or Stamina Mead as backup.
💡 Pro Tip: Before the fight, use a Hoe to raise the ground around the altar to create a level platform. This removes the water slowing you down, prevents the Wet debuff, and gives you room to dodge the poison cloud. This is the single most impactful preparation step.
5. Pre-Fight Preparation Checklist
- ✅ Iron Mace (Level 3-4) — your primary weapon
- ✅ Iron Sledge or Stagbreaker — for clearing adds
- ✅ Iron Armor or upgraded Bronze Armor — tank the melee hits
- ✅ Iron Buckler / Banded Shield — for blocking and parrying
- ✅ 3 Poison Resistance Meads — mandatory, 10 min each
- ✅ 3-5 Minor/Medium Healing Meads
- ✅ 3 best foods: Sausages + Turnip Stew + Serpent Stew (or Black Soup + Deer Stew + Queen's Jam)
- ✅ Hoe — flatten the arena before the fight
- ✅ Rested buff — fight near a sheltered campfire
6. Forsaken Power & Rewards
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| Reward | Details |
|---|---|
| Bonemass Trophy | Mount on Sacrificial Stones. Provides one of the strongest defensive powers in the game. |
| Wishbone | Equippable item that emits a pulsing signal when near buried treasure. Used in the Mountains to find Silver veins (critical for the next tier). Also locates buried Iron scrap in the Swamp. |
| Forsaken Power: Bonemass | Grants massive physical damage resistance for 5 minutes. Reduces Pierce, Slash, and Blunt damage taken significantly. 20-minute cooldown. The go-to boss-fighting and raid-survival power. Pairs especially well with heavy armor for near-immunity. |
7. After the Fight
- Equip the Wishbone and head to the Mountains
- Use the Wishbone to locate Silver veins buried under snow
- Defeat Wolves and Drakes for Wolf Pelts and Freeze Glands
- Prepare for Moder (4th boss)
← Previous: The Elder | Next Boss: Moder →
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