Lightning Bolt
This spell summons an invisible watchdog to guard an area. The hound is invisible to all but the caster, who may order it to keep watch over a particular area. The area must be close to the caster, however, for if the caster is more than 30 ft from the area the hound guards, it will return to the spirit realm. The hound can detect virtually any creature that enters the area: it can detect invisibility (which includes creatures on the astral and æthereal planes), can see creatures that are moving between dimensions, and can detect virtually any other method that might be employed to sneak into an area. If any creature larger than a cat or small dog enters the area, the hound will begin baying with its echoing, supernatural bark. Moreover, it will seek to attack intruders from behind (it does not make frontal assaults) and can attack as a monster of 10 HD for 3d6 damage, even if the opponent requires up to a +3 magical weapon to be hit. The hound cannot be harmed by any means other than by dispelling it.