The dungeons that the PCs will enter is under the control of the Mask of Illusion. This mask while powerful has an intelligence of its own. Only those worthy of understanding its capabilities may use it. One must defeat the mask before possessing it.
The map only shows the cave that the mask resides in. It is part of a remote collapsed underdark area. A hidden tunnel leads down deeper into the underdark and you may wish to use this as a side adventure. The dungeon itself is an illusion that the mask is creating so it will not be found. As the DM you should create the dungeon as you go insetting traps and creatures to engage and challenge the PCs. Be sure that the dungeon you create fits the open area of the cave.
The idea behind this that eventually the PCs will realize that the whole dungeon is an illusion. As the DM clues should be given to the PCs of this fact. One already has been provided for them being that the mask they are pursuing is the one with the illusionary powers. In the end the someone will see the reality of the dungeon and assist the others in disbelieving the illusion.
Clues to give to players:
1. Placing monsters in the dungeon that would not normally belong together, orcs being lead by a dragon for example.
2. When throwing a group of creatures at the PCs have them all look identical in armor, weapons, clothes, or even appearance.
3. Things such as no footprints in an old dusty corridor that the PCs know is frequented by monsters.
4. Halls and room changing directions or shapes.
5. Subtle things that you would find in a dungeon that you do not find here. A waste area, no ventilation system for air, or no foul stench.
6. Creatures mysteriously appearing behind the party for no reason.
7. Traps that seem to know their every move.
8. Things in place for no reason. For example a chest in the middle of an empty room.
9. Endless monsters and no lair for them.
10. If a player dies they will have no wounds or injuries. They died from the illusions affecting their mind. This also applies to the two corpses that will be found that were Shar’s men.
Using the only these type of traps below will perhaps assist in having the PCs realize that the whole dungeon does not exist.
Use these traps for the illusions:
1. poison needle (Fort DC 17 or die)
2. gas trap (Fort DC 17, or be paralyzed)
3. pitfall (Fort DC 17, 20′ deep spiked 5d6 damage)
4. spear trap (Fort DC 17, 2d8 damage)
5. fireball trap (Fort DC 17, 6d6 fireball)
6. lightning bolt trap (Fort DC 17, 6d6 lightning bolt)
1. The Entrance: This is the entrance to the cave. It will look like a dungeon entrance to the PCs with 2 simple huge closed stone doors (illusions). They are trapped with a lightning bolt trap as above.
2. The Cave: This is where the illusionary dungeon will try to kill the PCs.
3. The Mask of Illusion and Company: The only part of the dungeon that is real is where the mask is. It is the lair of a male and female basilisk (HP: 50, 52) MM 23 3E. A long time ago when this cave was open to the outside a small earth tremor occurred, removing the outside opening and collapsing part of a natural wall revealing the underdark. The basilisks lost their connection to the outside only to find new food in the underdark. Two drow scouts investigating the recent tremor and unaware of the new inhabitants stumbled on to the creatures. One was petrified instantly. The other drow in an effort to get away stumbled over the stone figure of his friend. Both fell to the ground with the 2nd drow’s fleshy body softening the fall of the stone statue. The crushed drow had the mask of illusion in his possession at the time and was killed instantly before he could be made food for the great lizards.