Originally posted by Ghevd:

Not 100% on this but I think finding a boss location runestone doesn't give you the closest boss to that stone. Just one that was predetermined in worldgen.

My moder was miles away. was like 3 days sailing. At night I would dock at the nearest isle set up a portal and head home until morning.

Later I found another stone and another moder which was way closer than the first I was given.