It was a fine harness and reins. The leather was soft and well tooled. The bit was so shiney one thought it could be silver. It looked like no bit and bridle that he had ever seen. Yet, it seemed familiar, like he had heard stories about this before.
"There is something about the outside of a horse…that is good for the inside of a man."
The local band of 'nasties' (goblins / orcs / whatever) lives in relative peace with the local population.
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.
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).
Next time the PCs are in the area they find themselves VERY unpopular with the townsfolk.