Possibly the result of some magic experiment gone wrong, the Roofers, or Stinging Spider Dogs, live in the city since time immemorial. Authorities loathe them and offer 1 gold crown per fresh carcass. You'll soon discover why.
Roofer are nocturnal animals and live in family groups of 4 to 12 individuals. They are omnivorous, hunting for small rodents, birds, insects and scavenging for fruit, seeds and other human-related imports. Thy're filthy, mangy creatures, impervious to disease but ideal as disease carries.
Thy can run on their dog legs or crawl with the spider ones, climbing any kind of surface. When the spider appendages are not in use they are retracted under the belly in a dark, hairy cluster that makes them seem even more pot-bellied than they naturally are.
Their name comes from the fact that they tend to hide under roofs, inide attics or under gutters, sleeping through the daylight hours in tight, furry groups.
Roofers are not aggressive towards humans, on the contrary: they'd be perfect pets. The problem is: when they're happy they have an innatural compulsion to sting their benefactors. Their venom causes severe drowsiness for 1d4 hours, not unlike a generous dose of liquor, followed by vomit and uncontrollable shivering for 1d2 hours.
In the slums of the city, the poorest and most deperate citizens use their venom as a free alternative to drugs and spirits. Some breed Roofers (who are extremely happy to comply), coming to live very short lives in a state of perpetual stupor. This is why the city authorities pay good money for their extermination.
Their call sounds like that of hungry kittens, but they use it rarely, having adapted at being hunted. They're clever and see perfectly in the dark.
Roofer: 1HD, AC6 (fast), 2 attacks: bite (1d3 - 35% of contracting some disease) and sting (save vs. poison or see above, starting in 1d4 minutes), experience 50, treasure none, saves as small animal (dog).
New Class: Roofer Hunter - progression as thief - HD 1d6 - climb as thief - move silently as thief - hide as thief - resistance to poison (-5 to saving throws vs. poison) - immunity to disease - follows tracks in urban environment on a INT test - at 5th lvl gains 2 apprentices - at 9th lvl an office.
Trappings: small uber-faithful, smart, ferocious dog - sack - 10 feet pole ending with rusty hook.