The Rule of Six and Docility of Pokemon had existed as long as anyone could remember. At least, as long as most people could remember. The endless bloodshed and violence of the past, along with dangerous secrets, were buried long ago. The world was at peace, its meager inhabitants, blissfully ignorant, living in small, scattered hamlets with populations as low as six souls in a single village.
But there were a few who remembered. They remembered because their fathers remembered, and their grandfathers remembered. Their vigil guarded the world from returning to its natural, savage state. Even though the ancient origin of the pokemon had been lost even to these Four guardians, they knew the true nature of the beasts and what kind of destruction they could cause. They understood how thin the barrier was that suppressed the savagery, and they had vowed to protect it.
Long ago, the beasts wreaked havoc on humanity, slaughtering millions upon millions. The flora and fauna of the land was scorched and devastated. Helpless to fight back, what was left of the population hid in underground places and secret bunkers. The ancestors of the Four were the ones who ended the wars. They enslaved the monsters using forgotten techniques, turning the beasts on their brethren. Eventually the Four liberated several regions, enslaving the monsters and making safe the known world. Humanity emerged into a new world, the once vile beasts of destruction turned harmless.
The Four's technique made two key changes in the monsters. First, the monsters were made susceptible to a special device known as the Pokeball which was able to capture and imprison any beast of any size and remove the threat. The second change occurred when a beast was captured; a directive was implanted into the monster that forced it to obey orders from its captor.
The Four together had captured and enslaved hundreds of types of pokemon, and used them to enforce law and order amongst the tiny residual population. Other individuals certainly realized the potency of pokemon enslavement and began to use them for industrial purposes. Others began collecting the beasts in order to carry out their own agendas. The inevitable occurred, and soon the great pokemon wars broke out, killing a frighteningly large portion of the already tiny human population. The Four used their superior numbers and species of pokemon to end the war, but not before massive damage was done.
To make sure a pokemon war never happened again, the Four created a new law, the Rule of Six, making it illegal to carry more than six pokemon on your person at any given time. The Four also added a new directive to be implanted through the pokeballs; the directive forced a pokemon from causing death to any human or pokemon owned by a human. Eventually the Four was able to capture and implant the directive into every species of pokemon, and the Docility of Pokemon became. The directive was so strong that some of the more fearsome pokemon simply laid down and died, unable to cope with their loss of self. Others underwent massive brain trauma, permanently altering their vocal patterns, sometimes to sound freakishly human. However, the pokeball's method of directive implantation was eventually lost, and later iterations of the device were unable to implant any kind of directive. The devices became weaker with time, also, making it harder to capture stronger pokemon. It was all irrelevant, still, as the directive had already been spread to every known pokemon. The Four retained a secret collection of pokemon not affected by the no-kill directive, only to be used for great emergency. Every generation of the Four feared that it would be their generation that would be forced to unleash this last resort.
Generations passed. As it stood, pokemon collection and battling became popular hobbies for both children and adults, the memory of the once fearsome beasts lost in the sands of time. Nobody remembered the great destruction that almost wiped out humanity, or the pokemon wars that nearly wiped out humankind for a second time. Nobody knows why the Rule of Six existed, and nobody questioned it. No soul realized the true purpose of the Four, and no one knew that there were lands beyond the Four's control, still filled with ruthless, unaltered monsters. The secrets were guarded and hidden well, until one fateful year, when everything would unravel.