A group that wished to be 'ever-living' instead was cursed with 'never-dying'. Thier flesh rotted and fell fromthier bones but still they lived on. Now as skeletons they continue thier quest to remove thier curse. As skeletons they differ in that they do not need controlled or summoned. They are fully fledged NPCs with drives or ideas of thier own. Stabbing and slashing weapons would not affect them.
While traveling trough farm land the PCs come upon a merchant sitting on a wrecked wagon without a mule attached to it, hid face burrowed in his hands. He explains that he was robbed by petty goblins, unable to defend himself he had retreated. He asks the PCs to help him retrieve the mule before the goblins roast it, as a reward they may keep his goods. How hard can it be?