Void Devourer - By Bill Silvey

FREQUENCY: Very Rare 
NO. APPEARING: 1
ARMOR CLASS: -2
MOVE: Nil
HIT DICE: 6+6
% IN LAIR: 100%
TREASURE TYPE: A
NO. OF ATTACKS: 0
DAMAGE/ATTACK: Nil
SPECIAL ATTACKS: See Below
SPECIAL DEFENSES: See Below
MAGIC RESISTANCE: 75%
INTELLIGENCE: High
ALIGNMENT: Neutral Evil
SIZE: L (100' x 100')
PSIONIC ABILITY: 
Attack/Defense modes: 
LEVEL/X.P. VALUE: IX/525 + 3 per hit point

The dreaded Void Devourer is a bane not only for adventurers, but all who dwell underground, both good and evil. The Devourer has an insatiable hunger for the psychic energy or perhaps the dying screams of all it consumes. The Devourer is an extra planar creature which exists in both the Prime Material Plane and the Negative Material Plane; the only part of it that extends to the Prime Material Plane is it's "mouth", a cavern-like opening that appears to be a natural part of a dungeon wall. A Detect Magic spell cast upon it will reveal both powerful and evil magic.

If a victim enters the "cave", they find themselves in a maze-like area; any entry beyond the first few turns will almost certainly seal their fate. At that point the Void Devourer shuts it's "mouth" by withdrawing fully to the Negative Material Plane, and begins to toy with it's prey. 

Inside the Void Devourer, the victim will find themselves trapped in a constantly shifting maze, beset by lurking shadows, voices whispering horrible secrets, and what sounds like the screams of others trapped within - all merely illusions generated by the Void Devourer in an attempt to drive it's prey insane. The maze always changes it's layout, so mapping within the 10000 square foot space is impossible. Furthermore, a constant-effect Confusion spell permeates the interior of the Void Devourer.

Eventually, those unlucky enough to have become trapped within the Void Devourer will eventually starve or die of thirst, if they do not kill themselves first. For every week spent within the Devourer, even if ample food and water are brought or can be created (as by a Cleric) a Save versus Spells must be rolled for every individual within. A failure indicates the acquisition of an Insanity, as per the Dungeon Master's Guide. Eventually a suicidal mania will overtake those within, and the dreadfully patient Void Devourer will feed at long last.

The bones and belongings of it's victims are found deep within recesses, although the 'Devourer likes to manipulate a few choice objects near the "mouth" so as to entice prey to enter.

The Void Devourer may be attacked from within; although it appears to the touch to be solid stone it is in fact somewhat insubstantial. If the Void Devourer is slain, all occupants within must Save versus Spells or they will be flung into the Negative Material Plane with all predictable horrible results. The Dungeon Master may wish to have those within thrown to a different plane or realm on the Prime Material plane if they do escape. Note that Dimension Door, Passwall, Teleport and Dig spells do not function within the Void Devourer, but when they are cast they are lost!

Those who possess Psionic ability will innately sense the presence of the Void Devourer's evil intellect and know it to be inimical to all living things; if trapped within, the Psionically enabled can use Probability Travel to escape.

As a footnote, a Void Devourer cannot and will not attempt to "digest" anyone carrying a Portable Hole or Bag of Holding. Additionally, if a Void Devourer is struck by a Rod of Negation, it will immediately die. If this happens when it is "occupied", all within die with the Void Devourer unless a Save versus Spells is successful.