>>33511177The laser fired from the Ultimate Weapon hit an asteroid carrying an extraterrestrial virus causing it to mutate into Deoxys.
Not confirmed anywhere, but implied through Deoxys' rewritten Dex entry.
Similarly, the Ancient Kalosian war was fought between Unova and Kalos, another popular fan theory neither confirmed or even implied.
A different theory is that Lugia unintentionally summoned the thunderstorm which caused the lightning strike that burned down the Brass Tower, and this is why it fled and lives underwater.
