Dark Sun: The Scorched World of Athas
The withering ones are zombies that have been suffused with defiling magic. As such, they react violently when they are subjected to arcane magic. When a withering one is affected by a spell or some other expression of arcane power, it unleashes a burst of defiling magic from within it that washes over everything nearby. Though this wave of enervating magic can be dangerous on its own, the real peril comes when large groups of withering ones converge to surround a target. In such a case, the consequences of destroying one can be just as dangerous as the attacks the creatures make themselves. As a withering one succumbs, the explosion of magic that it gives off might precipitate the destruction of others nearby, which in turn give off their own death-dealing bursts of magic.
While withering ones, like other zombies, emerge from the undercity of Tyr in search of flesh, these creatures share an unending hunger for the flesh of arcane spellcasters. Despite the fact that these creatures react so badly to arcane magic, they have a ravenous hunger for wizards, bards, sorcerers, and others who have mastered the ability to manipulate arcane power. Worse, these creatures seem to be able to sense the presence of arcane aptitude within a person, driving them to pursue spellcasters over long distances.