How do I mark spawn points for Bonemass in the Swamp?

Marking spawn points for Bonemass in Valheim is a critical step for preparing to face this challenging boss. Bonemass is the third boss in the game and is found in the Swamp biome. To locate and mark its spawn point, you need to find a Vegvisir runestone, which reveals the location of the boss altar. These runestones are typically found in Sunken Crypts or near large stone structures in the Swamp biome. Once you locate the Vegvisir, interact with it to reveal Bonemass''s spawn point on your map.\n\nBefore venturing into the Swamp, ensure you are well-prepared. The Swamp is a dangerous biome filled with enemies like Draugr, Leeches, and Blobs. Equip yourself with poison resistance mead, a strong weapon like an iron mace, and a shield. Bring a bow and arrows for ranged attacks, as well as healing mead and stamina mead. Wearing iron armor or better is highly recommended to survive the harsh environment and enemy attacks.\n\nTo find a Sunken Crypt, explore the Swamp biome thoroughly. These crypts are recognizable by their green torches and iron gates. Inside, you will find muddy scrap piles that yield iron scrap, a valuable resource for crafting. While exploring, keep an eye out for Vegvisir runestones, which are often placed near the entrance or in larger chambers. Interacting with the runestone will mark Bonemass''s altar on your map with a red skull icon.\n\nIf you cannot find a Vegvisir runestone in a Sunken Crypt, search for stone structures or ruins in the Swamp. These structures often contain runestones as well. Be cautious, as they are usually guarded by powerful enemies. Once you locate the runestone and mark Bonemass''s spawn point, you can plan your approach. The altar itself is a large skull-shaped structure surrounded by a murky pool, making it easy to identify.\n\nWhen marking the spawn point, consider placing additional map markers for nearby resources or safe zones. For example, mark the location of a nearby Meadow or Black Forest biome where you can retreat to recover. You can also mark the path to the Swamp from your base to ensure a safe and efficient journey. Use the map''s labeling feature to add notes, such as ''Bonemass Altar'' or ''Swamp Entrance,'' for clarity.\n\nA common challenge is navigating the Swamp''s treacherous terrain. The area is often flooded, slowing movement and making it difficult to escape enemies. To mitigate this, build a small outpost near the Swamp''s edge with a portal linked to your main base. This allows you to quickly return if you die or need to restock supplies. Additionally, use the Hoe to level the ground and create paths, making traversal easier.\n\nFinally, before engaging Bonemass, ensure you have the necessary items to summon it. Bonemass requires 10 Withered Bones, which are found in Sunken Crypts. Collect these bones while exploring the crypts for the Vegvisir runestone. Once you have everything ready, return to the marked altar and summon Bonemass. With proper preparation and a clear map marker, you will be well-equipped to face this formidable foe.\n\nIn summary, marking Bonemass''s spawn point involves locating a Vegvisir runestone in the Swamp biome, typically found in Sunken Crypts or stone structures. Prepare thoroughly with poison resistance, strong gear, and healing items. Use map markers to note the altar and nearby resources, and consider building a portal for quick access. With these steps, you will be ready to take on Bonemass and progress in your Valheim adventure.