A single giant tentacle guards against intruders.
The giant tentacle's attack, if it hits you, will wrap its self around you and prevent you from moving. Every round after that if you are still in its grip, it will tighten its muscles. The damage this does increases by one for every time it happens. As a reaction if you attempt to attack it while it has a hold of you it will project an horific image and you must roll a mind check against 12. If you fail you lose any concentration and suffer a -2 attack bonus.
If you damage the tentacle while it has a hold of you, it will let go.