Quoted By:
Objective truth based on the code of the game here
mythical pokemon = event-only pokemon, if you can get more but the source still requires an event-only pokemon (see dusk Lycanrock, it can breed but the original ones were event-only) then it's still a mythical
(main) legendary pokemon = Mewtwo, Zygarde, the box mascots (minus Pikachu, Eevee, Charizard, Venusaur and Blastoise) and every mythical legendary pokemon
sub-legendaries = the others (including all UBs minus Cosmog, Cosmoem, Solgaleo, Lunala and Necrozma)
