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- "...if the Duchess Thax intends to strike, she'll give no warning… rather like the Zharan glass-snake! Delighted to see you again Duchess!"
"And you, Master Kenobi! I am glad the fates have brought us together."
- ―Obi-Wan Kenobi and Duchess Thax
During the Clone Wars, Thax was dispatched to the planet Themis to negotiate with the world's leader, Prince Lumon, for the supply of explosive ore from the moon of Themis. However, the Jedi Obi-Wan Kenobi and Anakin Skywalker also arrived in order to persuade Lumon to supply the ore to the Galactic Republic instead, but neither party was able to convince Lumon, who dismissed Thax and the Jedi.
In an attempt to discredit Kenobi, on the orders of the duchess, Thax's agent planted a droid onto Kenobi's starfighter, which sabotaged the craft and sent Kenobi and his vessel hurtling toward the explosive moon. The sabotage created the impression that Kenobi was deliberately trying to destroy the moon and Thax used that to persuade Lumon that the Jedi were fanatics who would willingly risk the lives of the prince's citizens for their cause. Kenobi's fighter was subsequently destroyed by Lumon's security forces, but the Jedi Master survived and returned to Themis with a scrap of the droid that had sabotaged his vessel. When Kenobi confronted Lumon and Thax with evidence of Thax's deceit, the duchess held Lumon at blasterpoint and threatened to kill the prince if Kenobi tried to move toward her. However, Skywalker used his lightsaber to disarm her, and Lumon subsequently expelled Thax and her Separatist delegation from the world.