Years passed after the creation of life. Human beings, the companions of Pokemon, emerged. At this point, your kind were little more than hunter-gatherers, dependent on the whims of fortune for survival. But already you were beginning to invent, to develop tools and recruit pokemon to aid your tasks. But the Legendaries were not content to just watch. We grew restless, eager to test out our powers rather than simply fulfill one task and sit on the sidelines. For this was the First Age, the Primal Age, when there were very few rules or checks on our power. We Legendaries roamed freely, carelessly altering the shape of the world based on our whims. We would soon discover that such lax behavior would have dire consequences.
It was Dialga and Palkia, those who had the greatest power and the greatest responsibilities, who inadvertently caused our fall. They were rash and careless, using their powers for entertainment rather than the greater good. Dialga would travel freely forwards and backwards in time, each jump tearing the timeline apart a little more, until at last he had created an entirely new dimension. Now, there was the possibility of alternate timelines. For every action we took, there was now another parallel world where a different decision had been made. Entire cities and nations that exist in one timeline could be completely different in another, or not exist at all.
Dialga's carelessness certainly did make the universe more complicated. But it was Palkia's blunder that truly began the fall. In those days, Palkia was fond of tearing open rifts in space, travelling instantaneously across the universe, even creating pocket dimensions to enjoy. But such spacial distortion caused the walls of the universe to crack; and through those cracks seeped an ancient enemy: Chaos.
The primordial consciousness had grown ever more spiteful while Arceus created their universe; now, Chaos had a way inside. While it was still too weak to directly assault the universe, it could still influence the beings of the universe to do its bidding. And so, the destroyer locked its sights on the third of the Creation Trio, Giratina.
Giratina had, until this point, avoided the temptations of his brothers. While he had experimented with his powers, he had not dared to tamper with that which was already made; rather, he tried to create new forms of matter, new elements and compounds. His newest invention was a substance known as anti-matter, which upon encountering regular matter violently consumes it in a burst of energy. Giratina had deemed it a dangerous fluke, and resolved never to create it again. But then, the shadowy tendrils of Chaos wrapped themselves around Giratina's mind.
"Why does the master of matter, creator of every particle in the universe, bow down to anyone?" the voice asked.
"Arceus is my Lord and creator," replied Giratina. "I can not defy their wishes. To do so would break the natural order."
"But there would be no order without you. You are the most powerful of your brothers. Why not show the universe your greatness?"
"I cannot. We have set events in motion, now we must let them do their work."
"You would simply sit and watch? You are destined to command, to rule. You created the atoms that comprise every living creature. They belong to you."
For a time, Giratina resisted the temptation. But as these thoughts wound through his mind, the lure became too great. Blinded by lust for power, he sought to rule the universe as its chief creator. The other Legendaries dismissed such a desire as blasphemous, and forbade him from creating any new matter or interfering in the affairs of the universe. Enraged and encouraged by the voice of Chaos, Giratina began to wreck havoc and destruction upon the universe, creating antimatter to destroy the work of creation.
In the end, Arceus themselves descended from the Hall of Origin to intervene. With a single word, Giratina was restrained and his mind cleared.
"Why do you destroy that which before you created?" Arceus asked.
"I was forced into this role!" Giratina spat. "You would not let me be a leader, so instead I must be a destroyer."
"No one forced you upon this path, Giratina. You expected power, and when it was not granted you went into a rage. Do you truly believe that your purpose lies in destruction and power?"
"The universe needs a guiding hand to set it right!"
"When I first brought you and the others into the universe, I designed you to be inventors and creators. You were to create for the sake of creation, to be my grand architects. I expected you more than anyone, Giratina, to understand that creation does not need its maker to control it for eternity. If a seed is planted and the rain waters it, does anyone need stand guard over it? No. It will grow and mature and bear fruit, regardless of your presence."
"I… I desired more. I wanted to be like you! Adored and thought of as a god!"
"Godhood does not mean power. It means the wisdom to have power and not use it." Raising his voice, Arceus proclaimed, "My children, you have failed me. Dialga and Palkia, you have abused your powers and made the universe unstable. And you Giratina, you caused chaos and destruction. All three of you shall face consequences."
With that, Arceus extracted a portion of Diagla's, Palkia's, and Giratina's power, solidifying them into three orbs, which were soon hidden. Then, Arceus took one of the pocket dimensions created by Palkia, filled with various distortions in space and gravity, and sent Giratina into it. This Distortion Realm would be the home of all spirits who acted in life as Giratina had. And the former Lord of Matter, stripped of his power to create and left only with his antimatter, would be both the warden and prisoner of this realm. So it was decreed, and so it has been for centuries.
There is one silver lining to this tale. Isolated from the influences of Chaos, Giratina has since gained clarity and shown remorse for his past actions. He performs his duty as warden with a watchful eye, and has even prevented the destruction of the universe on several occasions by trapping various malevolent beings. The time may soon come when Giratina, reformed, will depart the Distrotion Realm for good.
When coming up with the ideas for this mythology, one of the biggest hurdles I had to overcome was Giratina. To me at least, it makes very little sense to have one of the three first beings you create, those who would define the laws of the universe itself, be someone who creates the opposite of what usually fills the universe. Therefore it made sense to me that Giratina originally had control over matter, and then became a Pokemon of antimatter after his corruption and fall.
Many people like to say that Giratina is the Pokemon devil. However, while its design is very spooky (ghost type really coming into play), it never does anything in the games that seems truly evil or devilish. Rather, I believe Giratina is more like the god Hades from Greek mythology: a misunderstood warden of the dead. Rather, Chaos in this story is more like the devil on the shoulder, whispering suggestions that cause destruction and misery.
One final note that I'd like to mention is the nature of evil in this mythology. Some people argue that people are naturally bad and must work to become good, others think that there's some external force that makes us do evil. In this case, there's a bit of both. Yes Chaos gives Giratina the temptation to misuse his powers, but at the same time it is he who ultimately chooses to go on his rampage. Additionally, Dialga and Palkia's selfish choices can definitely be considered bad, even before Chaos is able to manipulate people. Furthermore there are many actions that fit into a moral grey area. Yes, catching and training Pokemon to battle may be seen as cruel by some, but to others it's a way to make them stronger and more likely to survive than they would in the wild. And hey, the Pokemon games would be pretty boring if you couldn't catch Pokemon. Now, forcefully breeding Pokemon to produce a perfectly strong specimen for the sake of competitive battle? I'll leave that moral conundrum to you.