Brainiac: First appearing in Action Comics #242 (July 1958), Brainiac was a bald, green-skinned humanoid who arrived on Earth and shrank various cities, including Metropolis, storing them in bottles with the intent of using them to restore Bryak, the planet he ruled. He was accompanied by a "space monkey" named Koko. Cover to Action Comics #242, Brainiac's first appearance. Art by Curt Swan and Stan Kaye.While fighting Brainiac, Superman discovered the villain had previously shrunk the Kryptonian city of Kandor. He was able to restore the Earth cities to full size, but the Kandorians sacrificed their restoration to help him. Superman stored the city in his Fortress of Solitude, vowing to return the natives to full size. Brainiac's legacy was revealed in Action Comics #276, in a Legion of Super-Heroes back up story. This introduced the green-skinned, blond-haired teenager Querl Dox, or Brainiac 5, who believed himself to be Brainiac's 30th century descendant. Unlike his apparent ancestor, Brainiac 5 used his "twelfth level intellect" for good, and joined the Legion alongside Supergirl, with whom he fell in love. His home planet was given variously as Yod or Colu. In Superman #167 (February 1964) it was discovered that Brainiac was a machine, created by the "Computer Tyrants of Colu" as a spy. To increase the illusion that he was alive, he was given a "son", a young Coluan boy who was given the name Brainiac 2, but escaped. This was Brainiac 5's ancestor. It was later revealed that his name was Vril Dox, and that he went on to lead the revolt against the Computer Tyrants. It was in this story that Brainiac first appeared with a distinctive gridwork of red diodes across his head, later explained as the "electric terminals of his sensory nerves". This would remain his appearance until Action Comics #544 (June 1983), in which he was forced to create a new body, a metallic skeleton with a green, honeycomb-patterned "braincase". He retained his appearance until the Crisis on Infinite Earths.
Vril Dox
In the Post-Crisis DC Universe, Brainiac's history was dramatically altered. Vril Dox was now a radical Coluan scientist who, having attempted to overthrow the Computer Tyrants, was sentenced to death. In his last moments, his consciousness was attracted to Earthly sideshow mentalist Milton Fine, who worked under the alias "Brainiac". Needing cranial fluid to maintain his possession of Fine, Dox went on a murder spree. He discovered Fine had genuine psychic powers, which he frequently used on Superman. This version of Brainiac made his first appearance in Adventures of Superman #438 (March 1988). Brainiac was later captured by Lex Luthor, but used his powers to wrest control of LexCorp away from him. Under his mental domination, LexCorp scientists restored his Coluan form. The diodes in his head now increased and stabilized his mental powers, as well as allowing him direct access to computer banks. He continued to plague Superman, using a combination of mental powers and computer control. On one occasion he even returned to his pre-Crisis incarnation's city-shrinking tactics.
In the crossover story Invasion! it was revealed that, prior to its dispersion, the Computer Tyrants had allowed Vril Dox to clone a lab assistant. This was Vril Dox II, who would go on to form L.E.G.I.O.N., and (although he never uses the name) is the post-Crisis version of Brainiac 2.
The Doomsday Wars
During his latest skirmish with Superman in Metropolis, Milton Fine's body was irreperrably damaged, leaving Brainiac with only a short time to live. In order to preserve his life, he concocted an elaborate scheme. He had an agent of his, a Coluan named Prin Vnok, use a time machine to travel to the most inhospitable time in existence, the End of Time itself. His goal was the rescue of Doomsday, who had been left there by Superman and Waverider to ensure that he would never be a threat again. Seconds before the forces of entropy destroyed Doomsday forever, he was taken to safety by Prin Vnok and returned to Colu. There, a terminally wounded Brainiac transferred his consciousness into Doomsday's body, temporarily becoming the most powerful being in the universe - a genius psychic mind inside an unstoppable, indestructible titan. However, Doomsday's own raging mind would eventually overwhelm even Brainiac's will, forcing him to find another host body. Although Brainiac attempted to clone a new Doomsday that he could fully inhabit, his efforts failed and he was forced to adopt a robotic body, dubbed Brainiac 2.5. He became briefly obsessed with gaining Superman's form.
Brainiac 13. Cover to Superman Y2K #1. Art by Jackson Guice.At the turn of the millennium, Brainiac revealed he had placed a sleeper virus in LexCorp's Y2K bug safeguards. This was intended to dramatically boost his abilities. Instead it allowed his upgraded future self, Brainiac 13, to arrive from the 64th century. B-13 began transforming Metropolis into the 64th century version of the city, which, apparently, he controlled. When it became apparent he was to be defeated by the combined efforts of Luthor, Superman and his own past self (now possessing the body of Luthor's infant daughter Lena), he gave control of the city to Luthor in exchange for Lena/Brainiac 2.5, whom he forced to help him escape. He returned to Earth during the Our Worlds At War crossover, in which Earth and its allies fought a multifront war against Brainiac 13 and Imperiex. Brainiac 13 claimed to be allying himself to Earth, but this proved to be part of a complex plan to regain control. His chief aide was "Leniac", a green-skinned teenager with "control discs" on her forehead, suggesting the diodes of earlier Brainiacs (and identical to the forehead discs of the "upgraded" Brainiac 5.1, in the Legion, and the Animated Series version of the original Brainiac). At the end of the war Brainiac 13 and Imperiex were both sent back in time, becoming part of the Big Bang, and Brainiac 2.5 was expunged from Lena, who reverted to infancy, although the discs remained.
In the upcoming DC Minimates action-figure line, Brainiac 13 is packaged with Battle Damaged Superman.
Brainiac 12
In Superman #200 (Feb 2004), Superman travelled into the future and battled Brainiac 12, learning that everything Brainiac 13 had done in the past had been designed to ensure things reached the point where Brainiac 13 would be created. B-12's defeat before his upgrade apparently reversed the advances B-13 had made to Metropolis.
Later stories have referenced Brainiac (not Tolos) taking Kandor from Krypton, suggesting that some of Brainiac's Pre-Crisis history is still in continuity; however, the exact details of this have not yet been explained.