Tentacle walls

Tentacle walls was an enchantment spell that turned a room into a trap.

Effects
The area of effect was a single room no bigger than a 50 ft (15.3 m) cube. The caster had to touch the inside of the room to cast this spell. Once the trap was set, any creature other than the caster larger than a typical rat (3 lb/1.4 kg or 0.5 ft3/0.014 m3) would trigger the trap upon entering the room. When triggered, six large, black, leathery tentacles emerged from the walls, floor and ceiling, evenly spaced around the room and able to reach the opposite surface. The tentacles whipped wildly about the room, striking at random until all occupants either left the room, died, or all six tentacles were destroyed. If any tentacle was intact when the room no longer met the triggering conditions, the trap reset and six fresh tentacles would appear the next time a creature entered the room. When a tentacle was destroyed, it burst into a puff of black smoke.

Components
In addition to a verbal component, the caster had to touch the inside of the room to be enchanted, and have a dried octopus tentacle.