This spell improved on skull watch in a number of ways. This version of the spell was able to discern creatures of above animal intelligence and would only trigger if an intelligent creature crossed its view. The area of effect remained the same (a 20 ft/6.1 m wide by 90 ft/27 m long corridor), but the spell lasted until the skull was triggered, deactivated, or destroyed. If triggered, the caster received a vision of what the skull saw. The detail was such that the caster could recognize the race or species and any clothing, armor, and weapons the intruder or intruders may have been carrying. The caster also knew the location of the skull that was triggered. If a skull was deactivated (by dispel magic) or destroyed (by physical damage), the caster knew a skull was out of commission, but not the method by which it was neutralized. Improved skull watchers could not be turned or moved without setting off the alarm. Once triggered, the skull turned to dust after giving its alarm and visual report.
A caster could create as many improved skull watchers as he or she had levels. The skull continued to operate even if the caster died and even if the caster subsequently became undead.