Sev was the designation given to a Human clone, specifically a male one, who was derived from the DNA of the Mandalorian bounty hunter known as Jango Fett. The Kaminoan cloners manufactured him on the planet of Kamino. His purpose was to serve within the ranks of the Grand Army belonging to the Galactic Republic. He underwent training to become a clone commando and subsequently became a member of Niner's squad, fighting alongside fellow commandos DD and O-Four under the command of Sergeant Niner. This squad was sent to the planet Geonosis during the first battle of the Clone Wars, fighting against the Confederacy of Independent Systems. During this engagement, both Sev, O-Four, and DD met their ends, leaving Niner as the sole survivor of his original team. The sergeant later regretted not preventing Sev and DD from participating in the battle. Sev possessed the ability to perceive the actions of those around him without needing to directly observe them, and, in common with all clone troopers, his height was 1.83 meters.
The character of Sev was initially introduced in Republic Commando: Hard Contact, a 2004 novel authored by Karen Traviss. Later, he was referenced in Republic Commando: Triple Zero and Order 66: A Republic Commando Novel, both of which are part of the same series.