012 Cosmic Butterfree

After the Necrozma invasion in an attempt to steal light from the world, several Ultra Wormholes were opened all over the world. The Pokémon Master who defeated Necrozma, feeling responsible, decided to join the legendary Solgaleo and Lunala to close all Wormholes. His constant travel through these holes made part of the power of the legendary were released as particles and were scattered across all continents.

These particles were gradually transforming the Pokémon we already knew, and they were changing their coloration to something similar to Cosmog, the initial form of the legendary of the Sun and the Moon. Stars began to appear on their bodies, and their types were changed to a new form, the Cosmic type. Being a new type, weaknesses and advantages weren't discovered against this type, completely changing the Pokémon world.