- "You saved me from making a very great mistake, Master Kenobi! Themis shall join the Republic, and all Separatists present shall be expelled."
- ―Prince Lumon, to Obi-Wan Kenobi
At some point in the Clone Wars, Prince Lumon received Jedi Obi-Wan Kenobi and Anakin Skywalker, as well as Separatist Duchess Thax for negotiations over the explosive ore of Themis's moon. Both parties wanted to convince Lumon to give them access to the moon mines and their ore, which could become a very valuable power source. As the negotiations progressed, Lumon grew exasperated by Kenobi and Thax's bickering and, as a result, dismissed them.
When Kenobi later took his starfighter, he lost control of his craft, which had been sabotaged by Thax's agent, on the Duchess's orders. Lumon immediately assumed that Kenobi wanted to force his hand by threatening to destroy the moon and Themis along with it. Skywalker desperately tried to convince Lumon that his former Master would never do such a thing, to no avail. Meanwhile, Thax was further trying to discredit the Jedi in the Prince's eyes, telling him that they were nothing but fanatics who were ready to sacrifice themselves and the Themian people for their cause. Lumon gave Skywalker ten minutes to stop Kenobi, if the young Jedi failed, he would order his fleet to destroy Kenobi's fighter. Before Lumon could carry out his threat, however, Kenobi requested Admiral Andor of the Themian Fleet to fire on his craft, to the officer's great surprise.
Back in Lumon's throne room, a safe and sound Kenobi gave the Prince the evidence of Thax's treachery: a piece of the droid that sabotaged his fighter. Furthermore, in order to make the culprit reveal themselves, he bluffed by saying that the Force could tell him who planted the droid. Out of fear of Kenobi's psychic abilities, Thax's agent admitted that he was responsible for the sabotage and that the Duchess commanded him to do it. With her treachery revealed, Thax threatened to kill Lumon if Kenobi tried to get any closer. Skywalker arrived right in time and disarmed the Duchess with his lightsaber. Lumon subsequently decided that his planet would join the Republic and expelled Thax from his world.