The Trannon District was a district located in Carannia, the capital city of the Outer Rim Territories planet Serenno, near the Carannia Spaceport. In 23 BBY, Sith assassin Asajj Ventress went to the district under the orders of Count Dooku to search for Jenza, Dooku's sister. She later went to the Portmaster's office located in the district to find out more information as to Jenza's whereabouts.
The district featured a greasy back alley which contained at least one deactivated droid. Close to the alley was a repair pod where one could feel the heat of several furnaces. Throughout the district, people could hear the roars of starships from the nearby spaceport. Inside the district was the Portmaster's office which was far from the spaceport. The office-controlled space travel to and from the local spaceport. Saffia, another city on the planet, was over a hundred kilometers away from where the office was situated.
In 23 BBY, a disk containing several recorded holomessages between Dooku and Jenza, Dooku's sister, was discovered in a back alley in the Trannon District. Dooku later tasked Ventress to find his sister. Ventress obliged and went to the back alley where the disc containing the recorded holomessages was recovered.
After exploring the alley and coming to the conclusion that Jenza would not come to the alley, she went to the Portmaster's office located in the district. Upon finding the office, Ventress destroyed CZ-94 and barged into the office where she mind tricked Yepa, the Portmaster's assistant to make a cup of caf in Saffia. She then interrogated Portmaster Raz Fellidrone as to where Jenza was. After looking at the security system monitoring Carannia spaceport and finding out a Crolute kidnapped Jenza before she could leave the planet for Coruscant located in the Core Worlds, she left the office and warned the Portmaster that if he told anyone about what just transpired, she would rip out his tongue.
The Trannon district first appeared in the audiobook Dooku: Jedi Lost, written by Cavan Scott and published in 2019.