ORIGINAL ARCEUS/RAYQUAZA SPRITE BY vinnyruby ON FUSIONDEX.ORG

At the beginning of time, there was naught but Arceus, and the Titans formed of his egg. Eventually, as time went on, the universe expanded and Arceus annihilated the majority of the titans. Few remained, residing on Earth where Arceus loomed and spectated, watching as human life began to form.

Alone, isolated, Arceus began to experience discontent. He decided that he needed something, no, someone to be beside him. He found a human, one Sato Sugi. Under the guise of a human woman, Arceus chose to bed this man, and so he did. Time passed and Arceus lived as a human, and eventually, grew pregnant. Time passed still and eventually, three humanoid children were born, christened Dialga, Palkia and Giratina.

Sato looked upon his children and realised that he had not bed a human, and Arceus revealed his identity. The God proclaimed his love of Sato and the human felt the same, however not long after, the Titans struck. Numerous beings, giants with no remorse or feeling, began to ravage the lands, and Sato watched as his children quickly became the same form of God that Arceus had been.

Seeing his home and children at risk, though a mere human, Sato chose to fight the Titans, miraculously slaying one after much struggle... Though it came at the cost. His wounds were great, and though Arceus had begged him to not fight, Sato succumbed to the Titans. His fight was not in vain, as Arceus' divine fury destroyed what was left of the Titans.

In death, Sato remained in Arceus' head, grief eating away at him over time before, finally, he went to extreme lengths to rid himself of the guilt. Forming a body, reminiscent of his own though taking a draconic form, he recreated Sato as best he could, and so was created SATO.

Arceus remained discontent, SATO was not the same, and eventually he had to admit that Sato was gone, dead. Long after his creation, and sooner after their daughter Giratina was banished to the Distortion Realm, Arceus gave SATO the role as Earth's protector. Over time, he resided over Hoenn. Over time, he created avatars in Kyogre, Groudon and, most obviously, Rayquaza.

He has not been seen in centuries, all records of his appearance dating far before Pokéball technology was first innovated upon in the Meiji Hisui period. It's unknown whether SATO ever existed, or if it was simply folklore that was accepted as truth. Regardless, it's romantic to think that even God could find love in a mortal...