Originally posted by FerrousAradicen:

Figure out your map seed then put it in here - https://valheim-map.world/

I too had a similar problem during the early life of Valheim and it turned out my world seed was bugged and didn't actually have the 5th boss spawn.

Thanks for that link. Jesus no wonder we couldn't find it. In our entire world there are only 5 boss stones in plains areas