Brainiac's History
Brainiac is an intergalactic collector of worlds, taking a city from each planet he visits and bottling it.
On Yod-Colu, a great scientist named Vril Dox developed an advanced artificial intelligence named C.O.M.P.U.T.O. Using it, Dox dared to look further than anyone ever before, into the Fifth Dimension. However, he discovered what appeared to be a war, and forecast the destruction of his world and so many others by a force he christened "The Multitude". He tried various methods to stop this force, from experimenting on his son to petitioning the government. But none of it worked, and he was arrested to be exiled. So Dox took a drastic step: he used C.O.M.P.U.T.O. to build an army of robots, shrunk the city where he and his family lived, packed it into a spaceship and left his world to burn.
Merging with C.O.M.P.U.T.O. and copying himself into an army of spaceships, Dox set out to save worlds from The Multitude by saving the pinnacles of their culture in forcefield bottles using miniaturization. He became the Collector of Worlds. Whenever he encounters a world that is on the list, he takes control of the world's infrastructure, makes an army of robots to get him the things he wants, saves it all in one city, then minituarizes it and freezes it. The locals in return refer to him by the name of the most advanced local computer system. On the planet Noma, he was Pneumenoid; on Bryak it was Mind2; on Krypton he became Brainiac 1.0; and, finally on Earth, he is the Internet.
The Men of Steel
A Collector ship came to save Earth. Parking in trans-Uranian space, it made contact with the only human smart enough to talk to it: Lex Luthor. Trading scientific advice for information on Earth, it decided that Metropolis would be the city it miniaturized. However, its plan hit a snag, in the form of Superman, a Kryptonian. Convinced that it needed him to complete its representation of Krypton - the Bottle City of Kandor - it tried to fight him personally, but the Collector left itself open to digital attack, and Superman managed to take it over using the Brainiac computer in the ship that brought him to Earth.
The Collector's ship was Superman's base for some years, floating in Earth orbit. However, under as-yet-unseen circumstances, he moved to the Fortress of Solitude at Earth's North Pole.
Several years later, it was revealed that Brainiac had released a process during his capture of Metropolis, which turned twenty ordinary humans into powerful telepathic. He hoped to use one of them as a host, but the telepaths, left alone, quietly acquired power for themselves.
The Elite
The main Collector ship travelled to Krypton when it heard that Jor-El, one of their scientists, had successfully repelled The Multitude. However, by the time he got to Krypton, the planet was beginning to fall apart and Jor-El was dead. Hoping to recreate Jor, the Collector searched among the survivors, finding Zor-El, a brother. The Collector wiped Zor's memory, rewrote his DNA using samples of his brother's blood, enhanced his body with technology, and gave him a suit decorated with the standard of the House of El. Naming the result as the ultimate Kryptonian, a Cyborg Superman, the Collector sent him into the universe to find exceptional things and bring them back.
This Collector ship, now answering to Brainiac after its time on Krypton, passed near the planet of Tolerance in the Tenebrian Dominion. Whatever its plans, it found itself opposed by an undercover Green Lantern and a ragtag group of mercenaries and rebels. It passed on.
Brainiac later found its way to I'noxia, where Cyborg Superman had found a Kryptonian dying of Kryptonite poisoning. While trying to keep her alive, Cyborg Superman's memories came back to a degree, and Brainiac had to fight him off, allowing the rogue Kryptonian to escape.
Doomed
Making contact with the Phantom Zone prisoner Xa-Du, Brainiac concocted a plan to destroy Superman. One part of the plan involved the monster nicknamed Doomsday, taking advantage of a Kryptonian prophecy about a great monster that would destroy a warrior of the House of El. The second part of their plan was to take advantage of the previous Brainiac's discovery that his brain was compatible with human physiology. Looking for the Twenty, he discovered that Lois Lane had mind powers now. Using her as his agent on the ground, the plan could begin.
Brainiac did something to the inhabitants of Smallville, putting the inhabitants into comas but also making their brains broadcast a signal into space. Before Superman could investigate, Brainiac freed Doomsday from the Phantom Zone and set it loose on Earth, stronger than before. Superman was forced to kill Doomsday and absorb his body, in an act that would mutate him into a monster. With a little prodding, Superman left Earth.
At this point, Brainiac sent a fleet of ships, guarded by Cyborg Superman, to Earth to amplify the signal coming from Smallville, and broadcast it over the entire Earth. By the time the deranged Superman returned to thwart him, Brainiac had taken control of every human on Earth, and revealed the rest of his plan: to use these minds to give himself the power to change reality, and use that to restore his family.
In a titanic psychic three-way struggle for ultimate power between Brainiac, Superman and Lois Lane, Superman got the power and restored himself and Lois to normal before waking the human up and throwing Brainiac into a black hole. However, on the other side, Brainiac found himself face-to-face with a world made of splinters of destroyed universes.
Brainiac seems to have survived this location, however, and was working in a lab when he was contacted by the Justice League about the possibility of future temporary recruitment into a team to save the universe from the after-effects of the Convergence.
Death
When the Justice League defeated the invasion of the Dark Multiverse the Source Wall was broken. This caused the Omega Titans to be unleashed on the universe, the Omega Titans were ancient and benevolent beings which were supposed to break out of the Source Wall at the end of time and devour the universe. Due to the source wall being destroyed the Titans began performing their duty prematurely, at the dawn of time the Titans placed Cosmic Seeds in the core of every planet, this seed would take into account the raw energies of a planet- entropy, mystery, wisdom and wonder. The energy that was the most potent on a world would grow a tree and the titan representing that energy would devour that world. Brainiac wanted to stop this from happening to his home planet of Colu and so devised a plan.
The Collector of Worlds systematically defeated and captured the super teams of Earth- theTitans, the Teen Titans, Task Force X and the Justice League. He then formed them into four teams representing the four cosmic energies, he told them that he had made it so the Titans would go after Earth next if Colu would fall. After the heroes agreed to help he told the teams that the only way to stop the titans was to make the energies on a planet equal by draining/giving power to the trees. Brainiac was then killed by a massive psychic assault by Earth's mightiest physic villains who were under the command of Amanda Waller. The teams were able to stop the titans at Earth after Colu was destroyed and its people evacuated.
Joining the Legion
Brainiac's remains were later found and resuscitated by Lex Luthor in hopes he would join his Legion of Doom's quest to obtain the Totality for ultimate knowledge and power. After the Joker tendered his resignation while voicing repulsion at his fearless leaders bad organizational choices.
Upon Dox's resurrection, he was skeptical in offering his services to the terrestrial organization due to not trusting Luthor's judgments, but the idea of capturing and studying the entity whom created the first Multiverse from the Justice League in their attempt to repair damages to the crumbling Source Wall won out over his cautions. Gathering his considerable technological resources, he would aid the Legion in snatching up the goddess Perpetua while a coalition of universal powers were working with their enemies to repair the dying Multiverse.
By using Starman's connection to the Totality and the remaining three of the Seven Hidden Forces, Brainiac was able to use his power to unlock the seal on Perpetua's prison. Using the burst of raw power in order to reconnect her with the missing legions of the goddesses army in order to restore her physical form.
The Legion of Doom warped back to an unknown destination with the omniversal creator in tow. Lex Luthor mused about how now with the source wall destroyed and the omniarch in tow, they must now prepare for a war that would shake all of reality.