We summoned Bonemass last night just as every 1 and 2 star creature decided to crawl out of the swamp. Really bad luck and we got wiped. Our portal was on the other side of a section of plains so getting back to our bodies turned into an adventure that also did not end well.
My youngest, who is the fastest of us reflex-wise, goes in alone with a second portal. Gets it setup to have Bonemass destroy it. He does it again, this time a 2 star draugr chases him and the portal goes dead as he passes through. The third time, he kites Bonemass out into the plains, circles back around and gets the third portal setup. This one stays.
We get our stuff back and move the portal to a "safer" location, but still no sign of Bonemass. It's now been a week in game time and he still hasn't come home.
I hope he's having fun.
Source: https://www.reddit.com/r/valheim/comments/q9mbq5/we_have_a_rogue_bonemass_wandering_our_server/