Ganthas was a cyborg whose organic component was a Mar'kak in the service of the former Goa'uld System Lord Mars. Mars' First Prime, Augustus, ordered Ganthas to take SG-1 to Mars' palace when they were first captured. He was later ordered for prepare Jack O'Neill to become the new host for Mars' symbiote, but was interrupted and killed by Daniel Jackson who used a phase shifting device he was given by Ulysses to drag Ganthas' body into a nearby wall. (SG1: "Fall of Rome 1")