T'Jon was an Ornaran captain, commanding officer of the Sanction, a vessel used to transport goods to the Brekkians in exchange for medication, called felicium, for a plague. He assumed command of his ship in 2357, and, by 2364, had made twenty-six voyages to Brekka.
That year, on his twenty-seventh voyage the ship ran into trouble. The USS Enterprise-D, which was near, offered assistance. They suggested beaming over a replacement electromagnetic coil, but T'Jon, who was barely able to pilot the ship due to his felicium addiction, was not able to install it. When the Enterprise-D attempted to beam the passengers to safety, T'Jon had the felicium beamed over first. Then he, another Ornaran and two Brekkians were transported aboard the Enterprise-D. He was more concerned with the drug than with the two crewmembers he lost when his ship exploded.
When the Brekkians refused to give up the cargo to T'Jon, insisting that the payment for the drug was lost with the ship, they began to fight, using their natural electric charge. T'Jon threatened Riker with the charge unless Picard helped them. Picard realized that the felicium was a narcotic and the plague no longer existed. Picard refused to repair the Ornaran freighters in the hopes that without the ships, the Ornarans would begin withdrawal from the drug. (TNG: "Symbiosis")