Karius was a Zeon pilot who served under Anavel Gato in the 302nd Patrol Squad during the One Year War. Other than Gato, he was the sole surviving member of the unit. In U.C. 0083, he rejoined Gato for the attack on the Earth Federation Space Force naval review at Solomon.

Spoiler

Utterly loyal to Anavel, Karius shares with him a desire to not just seek revenge but also justify their fallen comrades sacrifice during the war. While shown to be a talented Mobile Suit pilot Karius is mostly operating in a support role to Gato, ensuring his attack on the Naval Review is able to happen. Near the end of Operation Stardust, Gato ordered him to take Nina Purpleton to the Axis Advance Fleet. Nothing is known of his fate after Operation Stardust though it is assumed he remained with the Axis forces.