Exobytes were a type of nanotechnological machine constructed by the intergalactic supervillain known as Brainiac. In one version of history, he released these nanomachines onto the planet Earth with the intention of them copying the powers of all of the planets superheroes which he would use to empower himself. This led to a seeming alliance with Lex Luthor where Brainiac offered him the chance to rule the world. The villain led various supervillains against the heroes of the planet which brought about their defeat along with the death of Superman. However, Brainiac revealed his true nature and attacked the planet with the intention of conquering it whilst his exobytes had copied various superpowers. During this time, Lex Luthor allied with Batman and used a captured exobyte to imbue a person with superpowers who took the name Fracture. Learning that they could use the exobytes themselves, Batman travelled to the Fortress of Solitude and intended to use the Kryptonian technology to send Fracture back into the past with the canister of exobytes thus imbuing thousands with abilities that could be trained to fight Brainiac in the past. At this point, the Fortress was attacked by Brainiac's drones and Luthor betrayed his allies; taking the exobytes with him alone into the past after ordering the Kryptonian structure to self destruct.
Once back in time, he briefed the Justice League of America of the events of the future and sent forth exobytes into Earth's atmosphere where they triggered abilities in hundreds of beings. He then urged the League to train them to fight the coming threat of Brainiac. However, whilst some sided with the Justice League, others became supervillains leading to conflict between both sides. When Brainiac arrived on the planet during his intention to digitize it, he discovered that his own exobytes seemingly infested the atmosphere somehow and contained recorded data within them. This led him to using his harvesters to capture the Humans that were now infected with the nanomachines. Many of these newly generated superbeings were detained onboard Brainiac's vessel but were freed by either a supervillain or superhero whereupon they returned to Earth in order to embark on their new career.
Lex Luthor was responsible for conducting experiments on Smallville whereby he mutated the citizens through the use of Exobytes using the DNA of Doomsday. As a result, the town's citizens were in various stages of contamination leading to them turning into rampaging monsters hat destroyed Smallville.
Individual exobytes resembled insectile creatures that were actually microscopic nanomachines that could not been seen by the Human eye. Initially, they had no powers but had the potential to record and duplicate the powers of a superpowered being. A nanite was capable of killing an opponent by entering into their body whereupon it began digitizing them cell by cell that was the process by which they analysed their subject. After data retrieval, the exobytes were capable of attacking in a swarm in order to digitize an allocated target or infect them with an allocated virus.
Once introduced into a new host, they could imbue the recorded ability into the new individual thus making them into either a superhero or supervillain. Their nature also meant that they could be dispersed into the air in the thousands allowing an entire planetary populace to gain superpowers. The exobytes were often selected for their download type and imbued their powers into their host with their abilities determined from the nanomachine itself. They were described as being a marvel of technology as they drained and digitized any information allowing them to hold near infinite amounts of power.
Brainiac believed them to be the key to the future and held the power of the planet Earth. He believed them to be his rightful creation and the means by which he would conquer that world.
- The exobytes serve as the primary plot point to explain character generation in DC Universe Online by allowing new individuals to be made that possess powers of an Earth hero that were recorded by an exobyte.