During the Clone Wars, Teller served the Galactic Republic as a Republic Intelligence station chief with the rank of captain. He was one of the officers that debriefed Captain Wilhuff Tarkin after his escape from the Citadel with the coordinates to the Nexus Route. Under the oversight of Dodd Rancit and in association with Knotts, a subcontractor from Lantillies, he worked with loyalist beings on worlds that had joined or were occupied by the Confederacy of Independent Systems, training them to serve as resistance fighters for the Republic. In the war's final year, he was assigned to the Gotal moon of Antar 4, organizing the Gotal and Koorivar partisans into well-armed resistance groups.
At the end of the war, he expected the Galactic Empire to spare them from punishment due to their work for the Republic during the conflict, and appealed to his superiors in the Imperial Intelligence community to provide documentation and transport for their extraction. However, COMPNOR refused to cooperate, allowing forces under the command of now-Moff Tarkin to kill many of the fighters on Antar 4 along with former Separatists, which became known as the Antar Atrocity. This event angered Teller and shortly after being assigned to Desolation Station, which focused on research for the top-secret Death Star project, he deserted the Empire. With this disappearance, he created his own resistance cell to fight against it, while intending to inspire the creation of other rebel groups throughout the galaxy.
Their most notable action happened five years after the end of the Clone Wars. When Tarkin and Darth Vader visited Murkhana on an investigative mission, Teller and a few of his accomplices, including Anora Fair, hijacked Tarkin's vessel, the Carrion Spike. They killed the ship's captain and comms officer, along with two stormtroopers, before taking off. The Imperials forced Faazah, a local Sugi crime lord, to give up his ship to them, and attempted to stop the captured Spike. However, Teller and his crew got away. After the successful hijacking, the insurgents of the Carrion Spike went on a campaign of destruction against various Imperial targets, such as Galidraan Station. Their information was supplied to them by Vice Admiral Dodd Rancit, a member of the Imperial Naval Intelligence Agency. However, Rancit was revealed as a traitor and executed on Vader's orders.
The insurgents, led by Teller, carried out an attack on an Imperial convoy transporting important parts for the Death Star project. They were unsuccessful due to the arrival of Tarkin aboard a Star Destroyer. Teller escaped in a fighter when his attack failed, at the urging of his comrades. His insurgents who helped capture the Carrion Spike, and others, were captured and executed. Teller later tracked down Tarkin on his homeworld of Eriadu, where he followed him into the wilderness and was caught in a trap. He broke his ankle, and briefly conversed with Tarkin and his relative, Jova. After they finished, Tarkin and Jova left him in the wilderness to see if he could get out of it alive after nightfall.
- Tarkin (First appearance)