Carnor Jax was a Human male who was a Sovereign Protector in the Emperor's Royal Guard, later becoming a Sith Lord. His father was a Thyrsian Sun Guard who served the Confederacy of Independent Systems during the Clone Wars, and briefly trained Jax when he could in his youth. After the Galactic Republic was reformed into the Galactic Empire, young Jax joined the Stormtrooper Corps. He served with distinction, and was selected to be trained as an Emperor's Royal Guard. After a year, he passed the training with fellow cadet Kir Kanos, who became Jax's rival.
After the deaths of Palpatine and Darth Vader in 4 ABY, Jax continued to serve, under Grand Vizier Sate Pestage and Director of Imperial Intelligence Ysanne Isard. When Dark Lady Lumiya asked for a contingent of Royal Guards, Jax was one of the guardsmen assigned to her and she noticed his Force sensitivity, making him her apprentice.