Team Rocket made the ultimate Pokemon when they created Mewtwo, but they couldn't control its power, and the Pokemon fled. For many years, nobody outside of the higher ups in the organization and a few heroes knew of its existence. The original Mewtwo disappeared into the world and would remain a secret forever.
The original would never be seen again, but its younger sibling would be born several decades later in present-day Lavender Town. Mewtwo's genetic blueprint had been saved and sold by a Rocket Scientist, and attempted replica was created underground.
The first second Mewtwo to show promise for survival was cloned over ten years after the first, after hundreds of failures before it. It arrived to the child-stage when it's first show of Psychic activity happened. It began reaching out with its mind for others but seemed unable to connect mentally with anything. Even other Psychic Pokemon put into the room.
Mewtwo was searching on a specific Psychic wavelength for something, and ignored everything else. After a few days of this insistent searching it became distressed, the monitors keeping track of its brain activity began to go haywire. Scientists tried to sedate the Pokemon and stabilize it, but nothing seemed to help. The young clone began to fidget and twist around inside the tube, even banging against the glass at points. Within two hours of the first signs of mental distress, the Pokemon went into cardiac arrest and died.
An autopsy of the clone revealed that some of liquids in its body had changed, specifically it's blood, lymph, and cerebrospinal fluids. No one had altered the nutrients in Mewtwo's suspension tube, or appeared to have sabotaged the clone directly. It was assumed that whatever Mewtwo had been trying to do before it died had caused the change that killed it.
Nothing else appeared to have changed on the specimen, save for its eyes. Originally the Mewtwo had shared the same violet eyes as the original, but when they were looked at post-mortem, they had turned pink, and glowed even though the Pokemon had died.
The fluid and eyes were removed from the body for further examination, while the dead Pokemon was preserved and stored on a shelf in the main laboratory with the rest of its half-formed brethren.
The strange series of events that led to Mewtwo's early death came together in the following week. No one was in the room while it happened, but security camera's picked up a Spinarak crawling along the wall towards the shelf of Mewtwo fetuses. The bug Pokemon crawled up onto the developed child Mewtwo's large jar, and in a flash of light the mirage Pokemon Mew revealed itself. The Pokemon remained on the screen for several minutes, peering through the glass of the jar and seeming to show an expression of deep sorrow and mourning. It soon Teleported away, taking the dead baby with it.
Using the information gained from the video, it wasn't long before the scientists formed a hypothesis on just what the strange chemical that had killed their clone was.
They found that the chemical could be replicated when injected into Psychic Pokemon. The chemical would activate the Pokemon's Psychic abilities, causing it to send out similar waves that Mewtwo had. Eventually the waves would change the fluids in the Psychic Pokemon's body to more of the black chemical, and the Pokemon would die.
Having a steady source of the chemical, the scientists were able to start experimenting on other Pokemon, and eventually people.
Thirteen years after its initial discovery, an altered form black chemical began to appear above ground in the form of a new drug known as 'Cat Blood'.
This drug produced an effect of euphoria in people, followed by several days of numbness, the length of both effects depending on how much of the drug was taken. After the numbness fades, however, users are faced with extreme withdrawals that cause extreme agony. Body aches, internal tremors, severe headaches, a change in the color of the iris, and nightmares (often involving a specific Pokemon) are common side effects to the use of Cat Blood.
The chemical wasn't only distributed to junkies though, and vaccinations began to be laced with another version of the chemical. Those who received the chemical through vaccinations were only treated to the side-effects of the drug, though on a lesser scale. It was often written off as a reaction the the vaccine.
What was the point? The group of scientists were searching for specific reactions to the chemical, which still activated the strange Psychic wavelength in victims. These wavelengths were created by the baby Mewtwo to search out its closest genetic ancestor, Mew, due to its initial Psychic search for its nonexistent parent being unsuccessful. A similar reaction is caused in any other organism that's brain is affected by the chemical.
Human tests had showed that they too would search out for an ancestor, but not another human. People would Psychically link up to a Pokemon somewhere in the world, and their nightmares are actually that link, which activates best while asleep. People's eye color would change to the color of the Pokemon they are related to.
Like the original Mewtwo's glowing pink eyes, some humans eyes also glow. These people are connected Psychically to legendary Pokemon, and they are the reason for the mass distribution.
Noah Fulmine, a multimillionaire and CEO of the Olympus Company is the mastermind behind this operation. She is seeking the victims of Cat's Blood and the tainted vaccines to find the locations of the legendary titans she desires.
She seeks to capture you alive, but she's not the only one hunting you.