Tentacle walls enables the caster to enchant a single room whose volume is less than or equal to the area of effect. The spell activates 1d4 rounds after any creature other than the caster enters the room. The intruder must be larger than a normal rat; that is, it must be larger than one-half cubic foot or weigh more than three pounds.
When the spell is activated, six black, leathery tentacles sprout inside the room; the tentacles are evenly divided among the room's surfaces (for instance, if the room is a cube, one tentacle sprouts from the floor, one sprouts from the ceiling, and one sprouts from each of the four walls).
The whip-like tentacles grow to the length of the room and swing wildly. Each round, a tentacle has a 30% chance of striking a random creature in the room, inflicting 1d6 points of damage (save vs. spell for half damage). Each tentacle has AC 0 and 25 hit points. When a tentacle is reduced to 0 hit points, it disappears in a puff of black smoke.
If all creatures are killed or withdraw from the room, the surviving tentacles withdraw, disappearing into the walls. If the spell is activated again, six tentacles reappear; new tentacles are created to replace any destroyed previously. As long as one tentacle survives an encounter, the tentacles will continue to be replaced. Only when all six tentacles are destroyed is the spell permanently negated.
The material component is the dried tentacle of an octopus.