The Renegade was an independent freighter that used to trade with Dorin gas. The captain of the ship used to sell Dorin gas to Kon Uuln and other Kel Dor living outside Dorin.
There was an occasion where the captain delayed for a long time, and Uuln suddenly had less than two days of breathable atmosphere at home, plus one more day if the family used their masks. He tried to contact Dorin and ask for help, but Dorin could not provide him with atmosphere in less than four days.
Hopeless, Uuln looked for some friends of him that could help, asking them to find the captain and its cargo. The friends discovered that the Renegade was on planet, but her cargo hold was empty. The captain was missing. There were different options: The captain could have been kidnapped and the cargo stolen; a usurer with whom the captain was indebted could have taken both the captain and the cargo; one of Uuln's enemies could have bribed the captain to "disappear" until it was too late; or an oppressive, pro-Human government or faction could have arrested the captain with false charges to eliminate aliens in the planet.
Sources[]
"Alien Adventures" (original article link) on Wizards.com (content now obsolete; backup link)