Hello Daniel :)

I'm sorry about the issue you encountered.

However I don't have enough information just yet to find what caused the error.

Can you please follow http://brightrockgames.userecho.com/topics/118-how-to-submit-a-bug-ticket/

and add your outputs log here please ?

Thank you =)

Thanks for the report !
I had a look into it and I just found the culprit.
Expect a hotfix very soon : )

Hello : ) I'm sorry about the issue you encountered, and I'm really surprised that after a cache and integrity verification from Steam the DLL was still missing.
The Plugins folder should look like this:

In case this file is still missing, You can download it here, and copy it to E:/Games/Steam/steamapps/common/War For The Overworld/WFTOGame_Data/Plugins/

GalaxyCSharpGlue.dll

If it doesn't solve your issue please get back to me over here =) 

Cheers !

As Cian mentioned I will need a link to the map to be able to investigate further