Black Zero is a Kryptonian rebel group that started a civil war with the Ruling Council of the planet Krypton. In one of their most famous battles, Black Zero held their battlefield at the city of Kandor, with Major Zod leading the charge (Alia, Basqat, Coats, Faora, and Vala) against the rebellion.
The rebellion managed to destroy the entire city of Kandor, with the wife and son of Zod being caught in the catastrophe. For his loss, it gave Zod the strength to win the war, by 'driven them back to the ice and decimated their ranks' as he might say. And to work with Brainiac to destroy Krypton.
When Zod was in Kandor for the battle for Kandor he said the forces of Black Zero are closing in.
In the Comics
Black Zero is the name of several entities in the Superman mythos. The original was a super-villain directly responsible for the destruction of the planet Krypton. The Black Zero Organization was a Kryptonian terrorist group. They also developed the Black Zero Virus, a program that plagued technology in the Fortress of Solitude. There was a Black Zero Unit as part of the Kryptonian Military Guild. This was also the name used by Black Zero, an evil clone of Superboy. The name was first used by Otto Binder in Superman #205. (1968)
Original Black Zero supervillainThe original Black Zero appeared pre-Crisis in Superman (vol. 1) #205 (1968), in a story entitled "The Man Who Destroyed Krypton" written by Otto Binder with artwork by Al Plastino. This Black Zero revealed to Superman that he was a space saboteur who destroyed planets. He had been hired to destroy Krypton, and discovered that the internal stresses which would have destroyed it in any case were dying down, necessitating his involvement to ensure it exploded.
In the present day, Black Zero came to Earth, threatening to destroy it as he did Krypton. In desperation, Superman released Jax-Ur, a prisoner of the Phantom Zone, who wished to avenge Krypton's destruction. As he launched a devastatingly powerful missile toward Earth, Black Zero attacked Jax-Ur with a Red kryptonite bullet, causing his body to mutate wildly into several serpent-like forms. This proved to be Black Zero's undoing; While Superman saved the Earth from the missile, Jax-Ur transformed into a Medusa-like form, turning Black Zero to stone with his gaze. Black Zero's body was then shattered by Jax-Ur, in recompense for what he had done to Krypton.
This story suggests that were it not for something none of them knew, Jor-El would have been wrong and the Science Council right. E. Nelson Bridwell hypothesized that what Black Zero had noticed was the Green Lantern Tomar Re's attempts to prevent the destruction (as seen in Superman (vol. 1) #257 (1972)), meaning the two sets of interference canceled each other out, and Jor-El was right.
Black Zero had the ability to create "psycho-molecules" with his mind, which he could then shape into any form of matter he chose. His brain had been fitted with a plastic coating, preventing him from being hypnotised. He could make his body intangible, enabling him to pass through solid objects. He was a skilled engineer, able to create weapons and devices that could destroy entire planets. He was also skilled in the art of disguise.
Black Zero organizationsThe first post-Crisis version of Black Zero appeared in the 1988 World of Krypton miniseries written by John Byrne and illustrated by Mike Mignola. Although later described as a "clone liberation movement" in Superboy (vol. 3) #61, Black Zero was described as a "terrorist" organization that was ultimately responsible for the destruction of Krypton: in the Third Age of Krypton, Kryptonians extended their lives by maintaining clones in suspended animation (the Clone Banks), which they then harvested for body parts. Trouble in Kryptonian society concerning this issue emerged after it became publicly known that a prominent citizen raised a copy of herself in order to marry this clone to her own son. The enraged son publicly confronted his mother (after presumably killing the clone wife) and shot her, but was forcibly stopped from killing himself. After widespread public knowledge ensued concerning the fact that a clone was allowed to achieve full sentience as a living being, a new Kryptonian war began. Prominently featured in this war was the Black Zero organization, which acted against this "genetic slavery"; this began the War of Clone Rights, which lasted for a millennium. In their final act, Black Zero detonated a device that would later become known as the Destroyer. In essence, this device functioned as a giant nuclear gun, that fired a concentrated, sustained burst of nuclear energy directly into Krypton's core. Though subsequently destroyed by an ancestor of Jor-El himself, the Destroyer's effect would later be fully realized; It would cause a chain reaction deep within Krypton that would later obliterate the planet.
A second Black Zero group appeared in the 2005 graphic novel, Superman: Infinite City.Most recently, the name "Black Zero" was used by an elite Kryptonian military force, under the command of Ursa. This unit included Thara Ak-Var's parents. The unit, except for Ursa, was killed attempting to defend Kandor from Brainiac.