“ Darklings are a kind of Halflings living in the sewer of medium to large cities.
Even though they smell badly and are quite dirty, Darklings are friendly and clever.
They try to limit the knowledge about their existence to only a small number of trustworthy persons, including player characters.
Darklings trade in information. Money, weapons and magical items have no value for them. This is why they hide beneath the sewer grates, listening to all that is said in the city above.”
“ <br />
The local band of 'nasties' (goblins / orcs / whatever) lives in relative peace with the local population.<br />
Along come the PCs and go through their usual heroic monster bashing routine, wiping out the nasties and pinching all their stuff, then continue on their way.<br />
Problem is, they don't kill ALL he nasties. The survivors want revenge and, after spending a few months recovering, start to take it in their own inimitable style (which is not unlike that of the PCs come to think of it).<br />
Next time the PCs are in the area they find themselves VERY unpopular with the townsfolk.”