Dusts of death was a spell unique to Zakhara, the Land of Fate.
This spelled turned dust or sand into a deadly poison. The poison was undetectable, but casting detect magic revealed a magical nature about the dust.
If consumed, this dust instantly killed the consumer. The only trace of foul play would be a bit of dust around the victim's lips and nostrils.
Many sorcerous societies in Zakhara used this spell as their prime method of assassination.
This spell required a pinch of sand or dust to cast.