Jack: "You know, Cal, when we worked together, I always thought you were a reasonable guy-"
Kallis: "No you didn't and no I wasn't. You thought I was 'a cold-blooded psycopath' - they showed me the report you wrote."
Cal Kallis is a former Delta operator who was recruited into the Commander-in-Chief's In Extremis Force.
At some point prior to 2006, Kallis was assigned to the Commander-in-Chief's In Extremis Force.
When Judah was placed in charge of the mission to collect the pieces of the Golden Capstone hidden inside each of the seven ancient wonders of the world, Kallis was chosen to be Judah's right-hand man.
Tracking Jack to a mine in the Sudan, Kallis was part of an advance team, and located the swamprunners Jack had used. After he captured Jack's team, Kallis threatened to kill Zoe Kissane unless they handed over the Piece they had collected. After reporting to Judah, he was ordered to bring Jack to Judah and kill everyone else. However, when the European's attack allowed them the chance to escape, Judah then ordered Kallis to at least allow Jack and Lily, daughter of the Oracle of Siwa, to escape. However, Jack's entire team managed to get away.
After tracking Jack to Hamilcar's Refuge, Kallis and his team followed them through the main entrance and through the trap system. When Judah's team arrived, Kallis met up with them after they had retrieved the next two Pieces, and were ordered to finish off the rest of Jack's team using stinger missiles, only for them to escape again.
When Judah then led his forces to Jack's base in Kenya, Kallis was among his men waiting to capture / kill Jack's team when they returned on the Halicarnassus. But Doris Epper gave a subtle warning to Lily, who realised it was a trap, and Kallis tried to prevent them escaping. Although they did yet again, Kallis found Big Ears, who had been shot in the head but was still alive, and ruthlessly executed the young Irish soldier.
As Judah led a force to the Hanging Gardens of Babylon, Kallis and his men waited at the alternative exit, where they destroyed the Israeli's escape chopper. After surrounding Avenger and his men once they emerged from the Gardens, Kallis took the Piece from them, and coldly executed them on the spot.
Once the Americans had all of the Pieces of the Golden Capstone, Kallis was among Judah's men at the Great Pyramid at Giza to perform the ceremony. He worked to stop Jack's team from interfering, and after using all of his ammunition, fought Jack in hand to hand combat, easily taking the upper hand. As he gloated of killing Big Ears and finally getting the chance to kill Jack as well, Jack instead punched his metal fish through Kallis's nose. The barely conscious Kallis was dropped over the side of the platform, and his body was diced up by a crashed chopper's rotor blades.
Much like Marshall Judah, his commanding officer in the CIEF, Kallis is a cruel and sadistic man who enjoys killing people greatly, especially during his time as a Delta force assassin.