Cranium rat

Cranium rats (cephalic rats) are hive mind organisms consisting of a swarm of normal-sized rats, which have a somewhat unique appearance – the top of their heads appear to have been sawed off, exposing the brain to open air. In reality, the brains are not nearly as exposed as they appear – there is a tough transparent film covering the brain matter, stopping dirt and such from entering the brain easily.

All individual cranium rats are telepathically connected into a single shared consciousness. The more rats there are in a swarm, the more intelligent the shared hive mind becomes. There is a limit, however, and a swarm that gets too big will eventually splinter into two or more smaller swarms, each with their own hive mind. It is rumored that bigger swarms are frighteningly intelligent, far outstripping the thinking power of a single human being, but this is hard to confirm – cranium rat hive minds are very alien in their thinking, and find humans just as bizarre, making communication difficult. Regardless, the average swarm is clearly comparable to a human in intelligence.

Cranium rat swarms are powerful mind mages, and can easily survive the loss of as much as half of their component rats. This, coupled with their ability to spread their rats over large areas, makes eradicating them difficult. Fortunately, cranium rats don’t have any special animosity towards humanity – though not exactly friendly, the swarms are content to live and let live most of the time. The swarms also largely view each other largely as competition, so it’s rare to see two or more swarms cooperating on a single goal.

Aranea and cranium rats covet similar territories, and both specialize in mind magic. This has led to frequent clashes between the two species, which have been steadily going worse for the cranium rats as time goes by. This is partially because araneas have gotten proficient in structured magic as well as their innate psychic powers, but also because the aranea have been far more adept into recruiting human mages to help them against the cranium rats. As a consequence, some swarms have actually begun to share information between each other and coordinate their anti-aranean activities.