Make the Vibrating Square level into, rather than just another maze level, a level with 3 symmetric 7x5 chambers embedded in the maze, each with four exits, and a smaller 3x3 chamber at the bottom containing the upstairs. In the center of one of the 7x5 rooms is the Vibrating Square. This is intended to be a dark mirror of the Astral Plane.

Make the Castle a side branch, putting two down staircases on Medusa, one of which goes to the Valley and the other of which goes to the Castle branch, first preceded by several maze levels.

Levels between Medusa and the Castle generate with roving contingents of the Yendorian Army, and have large open areas if they are maze levels.