The Vow
The Vow is a binding pact between humans and Pokémon created sometime in Pokéarth's prehistory. It is what allows trainers to train mons, and (for the most part) keeps humans off the menu.
While the origins of The Vow are not certain, they might be tied to the legends and myths found in the Canalave Library. The myths essentially speaks of Pokémon having a purpose and living in harmony with humans; Man takes a Weapon and goes slaughtering Pokémon with it for no particular purpose, until he eventually finds himself alone. Then a mysterious figure appears (out of the void?) and chastizes Man for having deprived himself of the presence of Pokémon by his side. Man, distraught, forsakes the Weapon, and with it the mysterious Pokémon figure disappears into whence it came. It also talks of how Pokémon have committed to appear before humans in the tall grass of their own accord. WAAPT's "The Vow" is essentially a worldbuilding attempt to link these myths.
The terms of the Vow are what prevented the Seven Jerk Dragons from raising against humanity after the events of the Scolemis War in AU. They find a way to loophole abuse by turning all of mankind into Pokémon. Before them, an ancient Alakagross Civilization had been severely punished for endangering many species, among them the early humans.
(Confirm?) At some point it was suggested that the Armbands, in particular the Human→Pokémon one, were ways to explore The Vow.