Maxwell's Demon (3.5e Monster)

Maxwell's Demon
''A sinister brown hunched person stands before you, clenching and unclenching its modest claws and glittering gold in the sunlight. Upon closer inspection, you can see that it is actually made out of tiny wooden doors with brass knobs which constantly open and close.''

Membranous Form: When stretched across an opening, the Maxwell's Demon may alter the temperature and/or pressure of the two sides of the opening, by increasing one and decreasing the other. Doing so takes time dependent on the volume of the area beyond each side of the opening, independent of the volume of the area on the other side. Determine the volume of an area by accepting the first area with less than 1 square foot of ventilation leading to further regions (The Maxwell's Demon can eventually affect the further regions too, but doing so takes many times longer). A shift of one step takes 1 round per 5 ft. cube of space in the region. Once a region reaches the minimum temperature or pressure, it cannot be reduced further in order to heat up or pressurize the other region. When the Maxwell's Demon stops covering the opening, it generally takes as long for the environments to return to normal as it took for the Maxwell's Demon to change them.

Strategies and Tactics
The Maxwell's Demon prefers to block the only exit to a structure and kill everyone inside by burning, freezing, or suffocating them. When approached, however, Maxwell's Demons shift back into normal form, and use their Anti-Entropic Travel and Light Permeability to eliminate their foes with effective hit-and-run strikes. If they judge that hit-and-run attacks are ineffective or unnecessary, they either run away or use Permeable Flesh to slaughter their enemies in relative safety.

Lore
The original Maxwell's Demon was "created" by an enterprising Elan Cleric named Maxwell, who, over the many millenia of his existence, slowly became obsessed with defeating thermodynamics. When the third god he worshiped was slain by a Balor Wizard, the backlash ripped apart his slowly decaying sanity and he turned to the Abyss for inspiration. He achieved his goal when a scroll mishap after a particularly long night of research and combat transformed him into a Demon. Some say that he, the first of the Maxwell's Demons, is still wandering the Abyss somewhere.

Others say that this story is complete nonsense. Citing old adventurer's journals, they claim that Maxwell's Demons are called that because they were originally discovered at the surfaces of "Maximum Wells", wells filled with superheated air compressed to be denser than iron.

Typical Treasure
2d6 &times; 500 gp in items that can reduce entropy.

For Player Characters
As a creature with HD equal to its CR and reasonable mental stats, it may make an acceptable PC.