Zwil was a popular flavoring substance, added to cakes on planet Algara II. It had a taste of a mixture of vanilla and cinnamon. It had a weak narcotic effect on Drovians from Nim Drovis and it was very popular among them. It was ingested through membrane-lined breathing tubes in fist-sized plugs. About eighty-percent of Drovian soldiers were addicted to zwil.

The Shistavanen spicelord Volven Roxe was also addicted to a variation known as Drovian zwil, though he never traded it himself.