Demon Mutagen

The Demon Mutagen was a mutating agent used by Umbra during the late 15th Century in order to mutate humans and Pokémon into monsters, taking the form of a purple goo.

Origins

The Demon Mutagen was originally found by the Seel Yami and the Hydreigon Orochi, who used it to mutate into truly monstrous forms. At some point after destroying the Celestials and falling to Earth they met Umbra, who was able to produce the mutagen on a massive scale and used it to create a monster army.

Aftermath

After Umbra was defeated, the mutagen factories were destroyed in order to prevent the creation of more monsters.