Those messed-up creatures are Denied Arch-Demons inspired from an online RP.

Extremely powerful and, unlike ordinary Denied, actually real and conscious, those Pokemon Arch-Demons aren't the kind of Pokemon you'd want to befriend let alone meet at all... and considering they're powerful enough to tear apart a whole human city in minutes, it's better to stay the heck away from them.

Yes, in my stories, Mewtwo does create minions slightly more menacing and threatening than just a slightly darker version of Pikachu and Charizard.