>>27253439Arceus, the Creation trio, and the Lake guardians are the only Pokedeities.
All Pokemon were created through the extensive process of evolution. Mew being the progenitor of every single species is just a myth.
Powerful legendaries such as the birds, the beasts, the weather trio, etc. are just that: powerful entities who have withstood the test of time probably having evolved from a much weaker form. The mythological aspects of these Pokemon are probably hyperbolic if true at all. Think, for example, if the Loch Ness Monster was real, the type of pseudoreligious cult which would emerge around it because of how fabled it is. That's pretty much how legendaries work in the Pokemon world. It's like an Ancient Greek pantheon where some people would worship either Zekrom or Reshiram, and others either Xerneas or Yveltal, etc.