Antimon was the public Commentator (journalist) on Gallifrey at the time of Romana II's presidency. Antimon was filming at the Time Lord Academy with his robotic crew when a bomb explosion killed many of the off-world students, despite his attempt to raise the alarm. Darkel, an opponent of allowing these students onto Gallifrey, was suspected of involvement. Later, as the alien students were evacuated, a second bomb killed many more and destroyed Leela's K9 unit. Studying footage of the event, Leela and Coordinator Narvin discovered Antimon's involvement. Leela confronted him, but was knocked out by his droids.
In the chamber of the High Council, Romana and Darkel faced each other in an election, with the coverage to be broadcast by Antimon. Narvin was injured warning the Council that Antimon had booby-trapped the cameras. Antimon, through a voice-over, revealed he was an agent of Free Time and had only pretended to work for Darkel to his own ends. She had planned the bombings he carried out, but with different motives. He now intended to kill the entire Council. Just in time, Antimon was killed by the recovering Leela, avenging the original K9. (AUDIO: Imperiatrix)