4-SEN, alternatively referred to as Foursen, was a droid in the service of Gorry and the Mantellian Separatist Movement on Ord Mantell during the period of the Separatist War. He was positioned within the Separatist base's storage facility at Mannett Point when the smuggler going by the name of Ace infiltrated the base and eliminated several soldiers present.
Operating on the Galactic Republic's planet of Ord Mantell within the Bright Jewel system of the Mid Rim during the Cold War, 4-SEN was a two-legged droid with masculine programming. This droid was owned by a Human named Gorry, an affiliate of the Mantellian Separatist Movement. This movement was in opposition to the corrupt governing body of the planet, known as the Ord Mantell Central Authority, due to their allegiance to the Galactic Republic and sought independence. During 4-SEN's period of service, they were engaged in a civil war against the government and the forces of the Republic Army.
During a portion of the war, 4-SEN and Gorry were stationed on the Separatist-controlled island of Mannett Point. There, they were among the troops tasked with safeguarding the Separatist's personnel database, housed within a captured warehouse on the island. During their assignment, the smuggler known as Ace, aided by a Mannett Point local named Reki, infiltrated the warehouse. The smuggler's objective was to download all the data from the database to locate a Separatist named Skavak who had absconded with their ship and a shipment of weapons belonging to Rendia Freight. After dispatching several guards within the warehouse, the smuggler successfully accessed the database.
While the smuggler was in the process of downloading the data, 4-SEN's sensors registered the deceased guards, triggering a red alert status for the warehouse and prompting the droid to notify Gorry. However, the droid failed to detect any active threats, remaining unaware of Ace's presence as an intruder. The smuggler questioned Gorry about the last time 4-SEN's sensors had been calibrated, suggesting they were likely malfunctioning and dismissing the need for an alarm. Gorry concurred, and he and 4-SEN departed, enabling the smuggler to successfully complete their mission and escape.
4-SEN is featured as a non-player character in the video game Star Wars: The Old Republic, which was launched by BioWare in 2011. He appears in a single mission within the smuggler-class storyline. As a dark side option, players have the choice to directly attack and eliminate Gorry and 4-SEN instead of persuading them to leave.