Though often seen as little more than vermin by unsuspecting city folk, cranium rats represent a terrible menace when gathered in sufficient numbers. On its own, a single cranium rat is a negligible threat, barely more dangerous than a common rodent; but when they come together, cranium rats form a telepathic hive mind, and the more rats that gather, the stronger the hive mind becomes, eventually granting them superhuman intelligence and great mental powers.
Cranium rats serve an unknown purpose, gathering knowledge and ferreting out secrets for reasons known only to them. Some sages believe they are the eyes and ears of some dark deity of knowledge, such as Norgorber; others posit some connection with the illithid god-mind, Ilsensine. Those who pry too deeply tend to be found gnawed to death by thousands of tiny fangs. Despite this, cranium rat packs can be invaluable sources of knowledge for those who seek them out, for they know the darkest secrets of the cities they call home.
Cranium rats are creatures of the Great Beyond, found in vast quantities in the cities of the Outer Sphere – Dis, Yanaron, Pharasma’s Court, and of course, the Eternal City of Axis, where they congregate in vast swarms in the tunnels of Norgorber’s realm. They are less commonly encountered on Golarion, save in great cities with high concentrations of spellcasters, such as Egorian, Quantium, or the great cities of Absalom and Goka.
Shores of Swords 