Legends Arceus seed RNG manip tutorial
Ok because there's barely ANY tutorials online about this (and no, discord is NOT an archive of knowledge) ever since the switch emulators got nuked, I want to share the ideal way to RNG manipulate seed spawns on Pokémon Legends Arceus. Not outbreaks, but the seeded spawns.
So what you need is the game, a way to check your pokémons' IVs and abilities (e.g. PKHeX), some way to take notes or screenshots, and of course the pla-reverse-gui (on Lincoln-ML's github).
To maximise the chances of getting shinies you'll want to get perfect research on the pokémon and own the shiny charm.
In PLA the whole map of an area is seeded when you load in (you reseed by leaving to the village and returning to the area) with each spawner having its own seed. If you know the seed of a spawner you know exactly what pokémon will show up after you catch/KO the current ones on that spawner. There are multiple types of spawners, some will always spawn 2 pokémon, some always 1, and some will spawn an inconsistent number of pokémon, like 1-3.
These latter ones currently can't be RNG'd because we can't figure out the seed. Single 'mon spawners are just not worth it because there are no multiple paths to the pokémon generated so you will easily need some 60 iterations to get the same pokémon that you'd get in 10 on a double spawner.
Pokémon respawn when the time changes (e.g. from "morning" to "midday") or when the weather changes. Static alpha spawners take multiple time changes to respawn, I personally wouldn't bother with those.
Unfortunately you can't control the weather… or can you? Well...
I recommend doing this RNG manipulation during the quest to meet the lake trio. When you're ostracised from the village there is NO WEATHER at all to fuck up your respawns. You also don't have to talk to the fucking professor and go through multiple prompts just to leave an area. Life is much simpler.
Have autosave off for all of this.
Pick a spawner, let's use a triple qwilfish one here. Go to the area of it, bring 3 empty slots in your team, get near the spawner, and save. Catch all 3. You need to be able to distinguish future qwilfish from them so jot down some characteristics like gender, level, stats.
Reload. We will now discover what the seed finder calls pokémon 1. Catch/KO 1 pokémon, ensure the other 2 are still there and didn't run away or somehow despawn (happens A LOT with stuff like basculin). Teleport to camp. Rest/advance time, preferably to some other day time to prevent day pokémon from despawning into drifloons and fucking all of this up. Go back to the spawner, catch everyone there. One of the qwilfish will be different from the originals, that's your pokémon 1 and you can fill in its data on the seed finder.
Reload. We will now find pokémon 2 by basically the same method. Catch/KO 2 pokémon instead of 1, ensure the remainder doesn't randomly despawn, go rest to advance time, save when you get to the spawner, then catch everyone there. You should have an original qwillfish, pokémon 1, and a new qwilfish which is pokémon 2. These are iteration -1 of the generator.
If this is not the case then you got fucked over by a weather or time change or a 'mon despawned when it shouldn't, or you caught a pokémon from another spawner by mistake.
Fill in the seed finder data. Ideally evolve your pokémon if you're getting small ones so you can fill in multiple measurements to save on calculation time.
Seed finder will toss you a seed, put that into the generator as well as the filters you care about. In my case I have max shiny odds and want a shalpha fish with whatever stats.
If you didn't save AFTER catching pokémon 2, you can pick any of these. If you did save however (like to trade the pokémon for IV checking), you'll have to pick paths which start on 3, because you despawned everyone from iteration -1 and then iteration 0 will have 3 'mons.
You can open path tracker if you want to be anal and catch everything to make sure you progress correctly. But basically all you need is to follow the path and on each advance catch/KO the number of pokémon stated. So a person who saved after getting pokémon 2 will pick a path like 3-1-2-... which means now they advance time, go to spawner, catch/KO 1 pokémon, advance time, catch/KO 2 pokémon at the spawner, etc etc, until they catch/KO the last pokémon, advance time, and find at the spawner whatever it is they manipulated for.
Please note that alphas can't spawn near other alphas. If you want to manip for an alpha and there's one close enough to hear the alpha music in the spawner, then go despawn it before your manipulated alpha is meant to spawn.
Anyway enjoy your hunts! It's a slow but very easy to accomplish method and nearly impossible to fail. Also more relaxed than MMOs and allows you to catch "skittish" or "neutral" pokémon who you can't multi-battle like in the MMO RNG manipulations.