The Dungeon Master Zone is one of two positions on a Dungeon Dice Monsters board; either the white spaces used in normal gameplay, or the blue squares used in the advanced gameplay. These positions are where the Monster Lord figure or token is placed at the beginning of a game. However, they must both be on the same color space; if one player starts on blue, the other cannot start on white.
The Dungeon Master Zone to be used is decided largely by the number of monsters to be used; if both players have a total of 8 or fewer monsters and items between then, they should choose white, since it will be hard to to form a path far enough for the blue Dungeon Master Zones. If they have 10 or more, they should start on blue, since the inner space allowed for the white squares may not be enough for the larger number of paths created from summoning the monsters and items.