Drovian zwil was a potent variation of the drug zwil, produced on Algara II. The Drovians were one of only a few species to find the original form addictive, and produced this stronger version to suit their needs.
The Shistavanen spicelord Volven Roxe, in charge of the Outlander Club on Coruscant, was addicted to this drug, although he never traded it himself.