Sacreus was genetically engineered by Team Rocket to let them recreate the world in their favor; However, upon hatching, he was revealed to not have any of Arceus' powers besides levitation, and promptly escaped. While escaping, one of the members of Team Rocket shot a dart at him. He removed it after escaping and felt sick; He sought shelter at Viana's home, and the two quickly befriended each other. His belly began to grow steadily for about a month before holding at it's current size. Sacreus feels that the pregnancy just won't end, but he doesn't mind being treated nicely due to his condition.

Arceus and Pokemon (c) Nintendo