Zod (Callum Blue) is a militant general from Krypton whose physical form was destroyed by Jor-El (Tom Welling in flashbacks) and spirit imprisoned in the Phantom Zone. Zod makes his first appearance (Season 5) when Clark (Tom Welling) unwittingly releases him from the Phantom Zone. He succeeds in entering Lex Luthor's (Michael Rosenbaum) body only to be engaged in a battle with Clark who manages to get rid of him using the Kryptonite crystal belonging to his father (end of season 6). But Zod manages to finally and fully return to his physical form (season 8) with the help of the powerful Kryptonian Purple Orb, bringing with him hundreds of Kandorians, other Kryptonians, who are now scattered all over the globe.
Zod is by far one of the most dangerous and ruthless rivals Clark Kent has ever faced. He was a powerful general in Krypton, known and feared as a great leader and commander. Blinded by his lust for power and greed, he turned against the Krypton council and tried to set up a new order declaring himself as the ruler of the planet. Clark's father Jor-El (Julian Sands, various others) quelled Zod's rebellion and imprisoned him. Zod swore revenge and on being released from prison confronted Clark several times in a bid to conquer earth and enslave humans.
Zod is deadly, sadistic and cold-blooded with a single-minded agenda of conquering the world and exacting his revenge. On several occasions he tried to hurt Clark by turning his loved ones against him and threatening to harm them.
"Kneel before Zod."
"Better to rule in hell than to serve in heaven. Seeing as you love the humans so much, let's see if you fight like one!"