People of Brekka who kept the neighboring Ornarans dependent on felicium, a supposed plague cure that had become an addictive narcotic.
Brekka and Ornara share a star system. Generations ago a plague struck Ornara, and the Brekkians produced felicium, which treated it. The plague was long gone, but the Brekkians kept selling felicium, which had become their entire economy, and allowed the Ornarans to believe they were still sick.
In Symbiosis, the Enterprise rescued Brekkian and Ornaran traders from a doomed freighter. Picard and Dr. Crusher uncovered the deception, but under the Prime Directive Picard declined to reveal it, and instead refused the Ornarans replacement parts for their failing ships so the trade would end on its own.