It's Gen 8 Balanced Hackmons but with all the Pokémon in the National Dex.
Gen 8 BH had an inbuild issue of not having behemoths such as Primal Kyogre, Arceus and especially Mega Evolutions. National Dex BH unites these uncoded Pokémon and the new Gen 8 mechanics, moves, abilities and items. It's a BH spin-off, a very popular one at that.
For more about NatDex BH, read this.
