Legendary/Mythical RNG (CFW)

A guide for RNG manipulating Legendary & Mythical Pokémon in Pokémon Legends: Arceus.

In Pokémon Legends: Arceus all Legendary & Mythical Pokémon can have their internal values predicted ahead of time. By understanding how to predict upcoming Pokémon we can obtain any Legendary/Mythical we like with desirable IV & Nature combinations.

The method the game uses to generate Legendary/Mythical Pokémon varies so the RNG manipulation method used will depend on your chosen target. For the purposes of this guide the generation methods will be referred to as "Main RNG" or "Spawner RNG".

RNG Type Distinctions
Main RNG

Main RNG operates as a continuously and naturally advancing RNG state, requiring precise timing of the final inputs before the Pokémon is generated in order to achieve the desired outcome. Those experienced with RNG manipulation in other Pokémon games may find this method familiar.

Encounters
  • Dialga or Palkia - Origin Form
  • Dialga or Palkia - Non-Origin Form
  • Giratina
  • Regigigas
  • Arceus
Spawner RNG

Some Legendary Pokémon are linked to overworld spawners. In short, when loading into the map, these Pokémon are assigned a "Spawner ID." To advance the seed, the Pokémon must be knocked out and then respawned. Achieving the desired outcome requires respawning the Pokémon a specific number of times in succession until the target has been reached.

Encounters
  • Lake Trio - Uxie, Mesprit & Azelf
  • Weather Quartet - Tornadus, Thundurus, Landorus & Enamorus
  • Heatran
  • Cresselia
  • Manaphy & Phione
  • Shaymin
  • Darkrai

Setup and Installation

This section provides setup and installation instructions based on the type of manipulation you plan to do.
Important - Remove all mods and cheats for Legends: Arceus before proceeding. Mods/cheats can alter the RNG of the games and cause RAM reads to fail.

Switch mods/cheats are stored in the atmosphere/contents directory on your SD card. This folder is typically empty on a fresh installation of Atmosphère.

Methods for Disabling Mods/Cheats

Any of these methods can work to disable mods/cheats. You should select the best one for your use case.

  • Rename the atmosphere/contents folder to something else, such as oldcontents. This will allow you to keep everything you previously installed. You can simply rename the folder back when done.
  • Delete the atmosphere/contents folder. This may be a good option if you have many files in this directory that you do not recognize and you want to clean out your SD card.
  • Delete specific mods/cheats from the atmosphere/contents folder. This requires you to know which title ID corresponds to what.
  • If you wish to keep the atmosphere/contents folder intact, you can hold L every time you boot the game.
Required Software
Tools and Applications
Installation Instructions
  1. Download .NET 9.0 and run the setup wizard until complete. This is a required dependency for that allows our programs to function.
  2. Download LINQPad and run the setup wizard until complete. This will be used as an RNG tool for the purposes of this guide.
  3. Download and extract Sysbot.NET - Moarencounterbots into a fresh, empty folder. this will be used to track our RNG seeds.
  4. Download and extract PokeViewer.NET into a fresh, empty folder. This will be used to track our current RNG state.
  5. Download sys-botbase and extract the atmosphere folder to the root of your Switch SD card. This allows programs to communicate remotely with your console.
  6. Open the script that corresponds to the encounter you are targeting, open the Main RNG script if your chosen target is in the Main RNG list above and vice versa.
  7. Reboot the console into your chosen CFW environment, it is recommended to use SysCFW - NOT EmuNAND/EmuMMC.

Ensure that sys-botbase has been properly installed before continuing. You should see a folder named 430000000000B (sys-botbase) atmosphere/contents directory of your SD card if done correctly. Refer to the SysBot.NET Wiki (Troubleshooting) page if you are running into problems. Make sure to follow every step; this should resolve 99% of user issues.


Important - A direct download for Lusamine's SysBot.NET fork (Moarencounterbots) is provided above and should work perfectly for the purposes of this guide. If you wish to use the absolute latest commit you must build the project yourself by following this guide.

Figure 1 - Moarencounterbots Initial Setup

la-legend-1
Moarencounterbots Initial Setup
Initial Setup

Before doing anything else you will need to configure SysBot.exe to work for Legends: Arceus, this can be achieved by doing the following:

  • Open SysBot.exe at least once, then close the program. Doing this will generate a file named config.json.
  • Right click config.json and open it using your favourite text editor (e.g Notepad), you should see a bunch of settings that determine how the bot operates.
  • At the top of the page, search for a value named Mode and change this to 3 (Mode 3 represents Legends: Arceus).
  • Save any changes, then open SysBot.exe again, you should now see SysBot: Pokémon (LA) in the program header if done correctly.
Connectivity Confirmation

It is recommended to follow these instructions if you are not 100% confident that sys-botbase has been properly installed:

  • Open the Homebrew menu and press the Y button, note down the IP address.
  • In the SysBot.NET Bots tab, type the IP address into the assigned field.
  • Select any bot from the dropdown menu on the right, then click the Add button.
  • Open Legends: Arceus on your console and enter the overworld, then click Start All.
  • Look inside the Logs tab, you should now see your trainer information (OT/TID).

If you are running into issues communicating with the console, confirm that sys-botbase has been properly installed by following the installation steps listed above. Refer to the troubleshooting Wiki if you are still running into issues. Do not continue following the guide until the bot is able to interact with your console with no issues.


Great! - You should now have all of the required programs installed on your computer and have confirmed that sys-botbase has been properly installed to your console. Confirm whether your chosen target is generated using Main RNG or Spawner RNG by referring to the information at the top of the page, then continue following the relevant guide.
Continue to bot & script setup Main RNG Continue to bot & script setup Spawner RNG