Hi,
Is it still possible to go back to the mainland after entering chapter 4 on the island and underdark?
I still have some things to finish up there and explore, and I am unsure of when I will get back to the mainland.
Thanks
magnet

Yes, but it goes via the underwater city and underdark.

So, once I finish the city and work my way through the underdark, I will have the opportunity to go back to the mainland?
Thank you... BTW... is it the natural course of the game to take you back to the mainland or do I have to find someone to take me there?

Just keep playing, your path will lead you back to the surface. To tell you more would be to spoil you and I don't think you'd like that