Since the death of Prince Xizor during a skirmish on Coruscant in 3 ABY, the crime syndicate Black Sun had fallen from its old glory through infighting and had been keeping a low profile for decades. Somehow, they came under the leadership of Czethros, who aspired toward galactic domination. Part of his plan to defeat the ruling New Republic was to plant sleeper cells in positions of political, economical and military power.
Sleeper cells were also planted on the spice mining world of Kessel, which was being managed by the Sullustan Chief Administrator Nien Nunb. Among these sleeper agents were the Second Administrator Torvon and Kymn. During an assassination attempt on Nien Nunb in the carbon-freezing sections of the processing facility, Torvon was instead killed.
Meanwhile, at the Jedi Praxeum on Yavin 4, the andris spice addicted Anja Gallandro fled the moon on the transport Lightning Rod to retrieve a stash of andris hidden beneath the ice caps of the ocean world of Dac. In response, her Jedi friends Zekk, Jacen, Jaina, Tenel Ka, Lowbacca and his translator droid Em Teedee went after her on another transport Rock Dragon. During their mission, they arrived at Kessel where Jaina, Lowbacca and M-TD stayed behind to help Nien Nunb after hearing about the failed assassination attempt and that his workers were turning against him.
On a normal working day at the spice mines, a large cargo transport from Ord Mantell arrived under the pretext of carrying new office equipment including food supplies, recharge packs and atmospheric enrichment generators. Having docked, an exit hatch on the craft opened, and the captain strode out and greeted Nien Nunb, pretending to recognize him. He told Nien Nunb that he had brought a special surprise for him and told Nunb to watch him open the cargo doors.
When the door's of the vessels cargo bay opened, out came the surprise: an army of armed mercenaries. They charged down the cargo chamber firing their weapons in the air, creating much chaos and confusion. Even Kymn had drawn his weapon and shot at a guard near the communications array. The Black Sun sleeper agents also joined the newcomers in defeating the loyal workers and guards. Soon, Black Sun had captured the facility with little blood and Nien Nunb found himself a prisoner.
However, Jaina, Lowie and Em Teedee managed to evade capture and could only watched as Czethros himself arrived and rallied his followers. Over confident, he announced that Kessel would become his new base of operations where Black Sun could coordinate lightning strikes on the New Republic.
He also mentioned that he would use the planet's sophisticated transmitter to transmit messages to the infiltrators in the key governmental positions in the New Republic, ordering them to strike. Though small in number, their revolution would happen so quickly and so widespread that it would topple the New Republic. Following the coup, Nunb and his loyal followers were incarcerated at what remained of the Imperial slave barracks while many other workers and a few hapless cargo pilots were kept within force fields.
While hiding in the spice mines, the Jedi used Em Teedee to hack into the facility's computer systems, causing the fire-retardant and sewage containment systems to assault Czethros and his henchmen, distracting them temporarily. Later, when Kymn and two other henchmen entered a turbolift, Em Teedee froze it in place with an urgent clean-and-refurbish authorization code.
While hiding in an empty atmosphere factory, the Jedi decided that their primary mission was to sabotage Czethros's transmitter which he intended to use to send a signal to the Black Sun sleeper cells scattered across the galaxy. First, they needed explosives to blow it up. Second, they needed someone to plant the explosives. Em Teedee was selected for the job because his small size made it hard for him to be detected and he could hover.
During their exploration of the control rooms in the mine labyrinth, they found two packaged cylinders containing explosives small enough for Em Teedee's microrepulsorjets to carry. They attached these to the droid's casing using a special quick-release knot. The Jedi also encountered the alien smuggler and Black Sun lieutenant Lilmit who fled into his ship to hide from both the Jedi and Czethros.
Continuing with the mission, Em Teedee flew with the explosives towards the transmitter's vast dish and attached the explosives to its central control point. When the miniature droid was within a hundred meters of the transmitter and its guards, the transmitter exploded, thus ruining Czethros's plans to send out a transmission to the sleeper cells scattered across the galaxy.
Having accomplished that, the Jedi and Em Teedee went to free Nien Nunb and the other prisoners. On the way, they used their Force powers to overwhelm one of the mercenaries. With the prisoners freed, Nien Nunb and his workers rushed to the main armory and control chamber, where they armed themselves to retake Kessel from Czethros. In the control chamber, Nunb and Lowie keyed in commands into the computers there that blocked access to Czethros and his henchmen.
During the fighting, Nunb lured the treacherous Kymn, the captain of the cargo cruiser and their troops into a deep section of the mines and then sealed them with heavy plasteel barricades, keeping them out of trouble until the authorities arrived to arrest them.
Now all that was left was Czethros himself. Seeing that his plot had failed, he fled to the main cargo bay where he tried to persuade Lilmit to help him escape Kessel. However, Lilmit declined long enough for Jaina, Lowie, Nien Nunb and Kessel security troops to arrive. However, Czethros managed to escape on a turbolift down into the carbon-freezing facility. However, they still pursued him. Refusing to surrender and not wanting to be captured alive, Czethros fell into a vat of carbonite where he was flash-frozen as Han Solo had been decades earlier.
Later, the Chief of State Leia Organa Solo commissioned the thawing and interrogation of Czethros. As a result, the New Republic uncovered the Black Sun sleeper cells in the key governmental positions across the galaxy, thus desolating the Black Sun for over a century.
- Young Jedi Knights: Crisis at Crystal Reef (First appearance)