After killing Runhorn and the Dark Portal...

[Lancian]

Originally Posted by Zephiroth

I've just killed Runhorn and closed the Dark Portal but left some armies behind that I did not defeat, can I come back later and kill them? And all my troops are gone I had when my fight with Runhorn was won. They gone forever? Can I go back to the 4 islands?

Of course you can, you just need to finish certain quest first. Note: You can distant travel by boat only from Greenwort later on, not from Arlania or Wastes.