Bear Paw

Bonemass is a Swamp boss in Valheim. Its altar is found in the Swamp, and its location can be revealed by Vegvisirs found in Sunken Crypts and sometimes in ruined structures nearby. To summon it, place 10 Withered bones at its altar.

Bonemass is fought under a forced-rain environmental effect, so the arena is always wet and cannot be kept dry by moving the boss away. Its melee attack is a heavy close-range slam that deals up to 80 blunt damage and 30 poison damage to players, while also dealing 1000 chop damage and 1000 pickaxe damage to trees and rocks it hits. It also uses a poison cloud attack, leaning back before releasing a large green toxic wave that deals 100 poison damage in a wide area and lingers for several seconds, refreshing poison on anyone still inside. In addition, it periodically reaches under its arm and throws a mud ball that is not aimed at players; when it lands, it can spawn up to four random adds, usually Skeletons and/or Blobs. No further monster of the same type is spawned once eight of that type are already present.

Bonemass drops a Wishbone for each player and a Bonemass Trophy. Defeating it also unlocks the Bonemass power, which grants the player and nearby allies 50% resistance to blunt, slash, and pierce damage for five minutes. It also changes world events, disabling the Swamp night event with Draugr and Skeletons, while enabling Blob and Oozer variants of that same event, the Skeleton surprise event, and several other progression-dependent attacks. Defeating it additionally unlocks Skeletons spawning at night in the Meadows, Black Forest, Swamp, Mountains, and Plains.

• Poison resistance is the standard preparation for this fight. The Root Mask or Poison Resistance Mead reduces poison damage by 75%, and omitting that protection makes the fight much more dangerous.
• Bonemass and its summons are vulnerable to blunt damage and resistant to almost everything else. Clubs are the fastest way to end the fight.
• Stagbreaker and the Iron Mace are especially effective against both Bonemass and its summons.
• Pierce damage, including bows, is very poor against it. Frost arrows are only a partial ranged option and require Mountain materials.
• Running is often better than rolling when avoiding the poison cloud, since the roll can be too slow and costs more stamina.
• Its melee attack can be blocked, parried, dodged, or outrun, but a normal block may still leave the player taking poison and heavy stagger pressure.
• Flattening or raising the area around the altar improves mobility and can help keep Leeches from interfering.
• Bonemass can be safely handled from its altar and terrain features such as nearby trees or stone towers can be used for ranged attacks.
• In group fights, players should prioritize killing Skeletons and Blobs as soon as they appear. With larger groups, spreading out helps ensure only one player has to kite the boss at a time.

A common solo approach is to drink poison resistance mead, bring high-health food, and use a blunt weapon while staying close enough to exploit the weapon’s area damage. Bonemass is also vulnerable to sustained teamwork, since its summons can be controlled while other players keep pressure on the boss.