Crushing Walls

This spell enables the caster to enchant a floor, ceiling, or single wall of a room to crush intruders. The enchanted surface can be no larger than a square whose sides equal the caster's level times 2 feet (a 13th-IeveI priest could affect a 26' x 26' surface).
The spell activates 1d4 rounds after any creature other than the caster enters the room. The intruder must be larger than a normal rat (larger than one-half cubic foot or weighing more than three pounds). When activated, the enchanted surface moves toward the opposite surface at a rate of 3 feet per round. Unless the spell is canceled by the caster, the enchanted surface continues to move until one of the following events occurs:

• A creature with sufficient Strength (minimum score of 19) stops the enchanted surface from moving by succeeding a Strength check. Such a creature suffers no damage from the enchanted surface. If the creature prevents the enchanted surface from moving for three consecutive rounds, the wall returns to its original position and the spell is negated. If multiple creatures attempt to stop the wall, the highest strength score is used as a base score; one point is added to that score for every creature assisting. Thus, a creature with 16 Strength assisted by three creatures could attempt to stop the wall.
• A strong or heavy object made of stone, wood, or metal is placed in the path of the wall. If the item survives a saving throw vs. crushing blow, the object successfully braces the wall. If the object holds for three consecutive rounds, the surface returns to its original position and the spell is negated. The DM must use discretion in determining the types of objects that will brace the wall.
• Dispel magic or a similar spell or magical item is used to cancel the crushing wall.

Creatures can avoid being crushed by using a potion of diminution, potion of gaseous form, or other devices or spells that reduce size. The crushing wall almost never touches the opposite wall, usually being stopped by debris. A gap of two inches or more usually remains between the walls.
If the wall is not stopped, it causes crushing damage to everyone in the room. All creatures must make a saving throw vs. death. Those who fail are crushed to death. Those who save successfully suffer 5d10 points of damage. When the wall can move no farther, it returns to its original position and the spell is negated.

[Tome of Magic]

Sphere: Wards
(Enchantment)
Level: 6

Range: Touch
Components: V, S, M
Duration: Permanent until activated
Casting Time: 1 turn
Area of Effect: Special
Saving Throw: None

Material Components:
a 1-inch iron cube and a walnut shell