I'm not sure what you mean, but maybe this helps:
In Tunnels of Nechrubel you replace BASILISK!'s Special Rooms and Encounter tables with the new ones. When you find an entrance to the Tunnels of Nechrubel you decide on a direction of travel and move 'under' the board in a single direction, rolling on the 'Tunnel Events' table and moving your counter one space in your direction of travel until you have an opportunity to emerge.
And thank you - I am very glad you are enjoying it. It was sooo much fun to write!