So what if there was a legends Arceus nuzlock where to truly win, you gotta get Arceus. Now how do you get Arceus? By catching or evolving to save trouble of finding rare Pokémon. But in a nuzlock you can only catch the first Pokémon on each route or in this case section of the current biome you’re in. So how is this possible? Well the way you would do this is first, get your starter and do the catching tutorial, that’s 4 mons, at that point you can trade to do some Pokédex slots, or go ahead and do the story fast, if you can find a way to skip the credits, do that. Then go to beat Volo and get Giritina and then, only then, are you allowed to get any Pokémon you don’t have, and when you get Arceus you win, BUT, if any Pokémon on your team other than your starter faints(dies) then after getting Giritina in the post game, you have to catch another one but if possible, an alpha one.