The picture is not from the world where I completed the map. I used it just to show the cloudy area I was asking about.
As I was nearing the end of the map on a second world, I took the picture as I wanted to ask if some way to clear the area was still possible. On the first world, the 3 brothers are deposed, disappeared, or dead and I've moved on to the next map.
Oh well, maybe that's where the lunatic brother disappeared to.