I have been looking through various books with a dungeon being the main character however regardless of the book the character had to gain a physical body to forward the plot which i disliked. 

As a solution i got together with a friend and we decided that i would write the dungeon part while my friend wrote the part of a character who advanced the plot out of the dungeon.

What i wish to ask is how can we make organize the book while both of us write different characters?