Zeroes are, in the simplest terms, digital copies of a human being, created from the binary "ripples" a computer receives when that person is placed in
Netspace. The Zero usually possesses the original's loyalties and personality unless specifically programmed otherwise.
Each computer accessing Netspace shapes a
small area of it with its own data. Running a program in a computer will cause an object representing that program to form in Netspace.
When a person is placed in Netspace via a digitizer, their presence causes feedback that results in foreign code representing them to appear in the computer's memory as well.
The theory of Zero creation was, in short, to copy the foreign code representing a person, and paste it, and bring it to life, creating a digital clone of a human being, with all memories intact.
Zeroes are usually, and deliberately, less emotional than humans. The degree can vary, however- despite being clones, they are not 100% identical, and some may express a greater capacity for fear than others.
Upon dying, a Zero's body quickly destabilizes and disintegrates, leaving behind no trace. Similarly, limbs or hair that are severed will disintegrate in a short while, though these can be restored by using backup data later. The same principle behind these phenomena also causes Zeroes not to leave behind any skin oils on objects they touch- even without gloves, they leave behind no fingerprints provided their hands are kept clean.
Spoiler Warning - Major plot details may follow
The leader of
has long been obsessed with creating what, in his view, are the perfect humans,
as part of his goal to be a 'god', ruling over a world of his own design.
To this end, Team Galactic used stolen Netspace technology obtained from
Professor Kabili Sinclare to place their most loyal and efficient members in Netspace. Once inside, the short version of the theory would be that these members could, essentially, be infinitely copied and pasted inside the computer, and the copies would then emerge into Realspace. Once they found a way to perfect this, they could then move on to experiments in improving the mental and physical capabilities of the copies.
Team Rocket's own 'Two' series cloning projects, and the eventual shutdown of said projects, Team Galactic's scientists named their experiments the Zero project. The logic was that if the original was a 'One', and if an organic copy made of the same flesh and blood was a 'Two', then a copy that wasn't made of flesh at all would be a 'Zero'.
The first test subject -Erys Heritor- was killed during the copying phase- the data process of copying being applied to an organic individual had never been done before, and proved unsafe. Only 72% of her data was successfully copied before her entire physical makeup was destroyed, leaving only radioactive ashes remaining following the digitizer's retrieval attempt. All attempts to copy another living human were halted for the time being, while
Charon Baumtogh studied what had happened.
While researching other incidents of energy based life forms, in the hope that some existing Pokémon might hold the key to solving this problem, Charon learned that one scientist of virtually no renown professed to believe that
Darkrai was created from a human being, and was subsequently stripped of what little accreditation he'd had. After researching the history of Alamos Town, where Darkrai's first recorded appearance occurred, Charon soon came to believe as this earlier scientist had, finding records of an unsolved disappearance of a man whose hair, and even his clothes, resembled Darkrai's.
Had Darkrai been a human turned into a Pokémon, or a Pokémon who masqueraded as a human? Charon knew not the answer, but Team Galactic eventually managed to confront Darkrai, and obtain an energy sample from Darkrai's body. Upon studying it, Charon discovered that it did, indeed, have components with a structure resembling human DNA.
Digitizing the energy sample, Charon merged it together with the first Saturn's corrupted computer data. The result was amazing- indeed, Darkrai had once been human, but more than that, his current status as an energy-based life form meant he held the key to making more energy-based humans, and making the Zero project a success.
The first Zero produced took on the title of
Zero as a name. He proved to be fully human in virtually every respect. But unfortunately, in Cyrus' opinion at least, he was TOO human. Too emotional, too curious, too flawed. Nevertheless, Charon received permission to produce even more Zeroes, this time clones of Cyrus' personal bodyguards- the twins Venus and Terra. These clones were a success- Venus and Terra have since been cloned repeatedly, dozens of times, with these mass-produced, green-haired clone grunts forming the backbone of Team Galactic's forces.