You can solve that problem easily.

As already pointed out, you can check other swamps for locations of another Bone(less)mass spawn. Using a vesigvir won't help you, as it would tell you you've already found a boss location.

So you could use the Valheim world generator to load your map seed and figure out where another spawnpoint is.....

Or you can post your world seed here, as well as a screenshot of your current world map.
Other players can upload that link into the valheim world generator and tell you where you would most likely find another spawnpoint for that boss.


Thorin :)