PKHeX's shiny sprite collection is taken from pokesprite, which is licensed under the MIT license. PKHeX's Pokémon Legends: Arceus sprite collection is taken from the National Pokédex - Icon Dex ...
Over 20 Pokmon in Legends: Arceus are Shiny locked, making them difficult to obtain in Shiny form. The Legendaries, Mythicals, and starter Pokmon are among the Shiny locked species in the game.