Purrballs are found on several planets around the Frontier. They are small, long-furred creatures that can reach up to 45cm in length, and tend to be almost as wide as they are long.
Purrballs resemble slightly lumpy, fluffy balls with large-eyed, feline faces, though that appearance is misleading. Hidden under the fur, purrballs do have discrete heads and four very short legs with clawed feet (used for climbing trees when threatened). They have no tails.
Despite the feline appearance of the purrball face, purrballs are herbivorous, eating ground-dwelling vegetation, nuts, seeds, and fallen fruit. They live in small herds/family groups of up to 20 individuals. Generally, the group is led by the largest males, who compete for mates by puffing themselves and bristling their fur to it's maximum extent. Whoever is the larger is the winner.
A character encountering purrballs for the first time and observing their small size and slow speed (less than 2m/turn) would expect that they would be easy pickings for any hungry predator, but purrballs are not without advantages. Their large eyes give them excellent eyesight, and their sense of smell is considerable. While initial researchers were convinced that purrballs were deaf, later research revealed that their hearing is focused primarily in the infra-sonic part of the audio spectrum - purrballs are very good at detecting low-frequency sounds - and in fact infra-sonics are their primary means of communication.
Hearing, seeing, and smelling may allow purrballs to detect potential predators, but their most potent defenses are sonic in nature. The first is the "purr" that gives the purrball its name. The sound of a purrball purring is a natural hypnotic agent. Any character or animal within earshot of a purrball or group of purrballs must make a 1/2 LOG check or find themselves pacified and unwilling to attack the purrball. A critical failure on the check means that the hearer has actually fallen asleep.
Those that succeed in the check face a far more devastating weapon. When angry or frightened, purrballs can make use of a "second larnyx" to produce an excessively shrill and painful "scream". The scream, which is more than capable of shattering eardrums, causes the same damage as a sonic disruptor to any target in range. The purrballs themselves are immune to the scream due to their lack of ability to perceive it.
UPF ecologists are uncertain what planet purrballs originated on, or if they developed independently on multiple planets at once. In any case, it is thought that the world/worlds of origin were very lush, as it would require a densely-grown environment to support the development of purrballs in the wild. After discovery, many purrballs were taken off the planets where they were found as samples. Subsequently they were domesticated and have gained a following as pets.
Domestic purrballs are required by law to have a chip implant in their second larnyx to prevent them from screaming, but their purring abilities are left intact, as completely silencing them would be considered inhumane. A few citizens keep unchipped purrballs illegally as guard animals.
A domestic purrball costs 100-400 Cr, depending on breed. An un-chipped purrball costs 5x that at a minimum, and can only be obtained through black market sources.
(This creature inspired by the "fizzgig" from Dark Crystal, and by a picture of a particularly fat cat.)