I see many people talking about MOD's and I do not what they are. Can someone please explain what they are? Thanks!
Without changing the basics, you make new maps, stories, etc. Basically there's the main Arcanum engine, then the Arcanum story, maps, characters and weapons placed over it. Quite hard to make, though.
Just have a look around on the Terra Arcanum page - on the forums, I believe DarkUnderlord is the man to see?