This guide is meant to educate you with the first steps to modding this collection. You'll be extracting assets from the Unity game engine, some of these assets include the following read only memory images:

• https://datomatic.no-intro.org/index.php?page=show_record&s=46&n=1687
  
• https://datomatic.no-intro.org/index.php?page=show_record&s=46&n=1688
  
• https://datomatic.no-intro.org/index.php?page=show_record&s=46&n=1689
  
• https://datomatic.no-intro.org/index.php?page=show_record&s=46&n=1690
  
• https://datomatic.no-intro.org/index.php?page=show_record&s=46&n=1691
  
• https://datomatic.no-intro.org/index.php?page=show_record&s=46&n=1692

NOTE: The above denotes these were dumped from the Switch eShop using different tools called DevXUnityUnpacker and HxD, we'll be dumping from a different origin, namely the Steam game's local files, but they're the same images as identified by the hash data.

Additionally, you'll be able to extract other assets such as original music, wallpapers, and menu sprites / textures.

I want to stress that you should NOT be distributing these assets by any means, that is illegal.

So long as you understand this, you can extract the ROMs to play in a gameboy emulator or even mod them and rebundle them. You can also modify or even completely change the various aforementioned menu assets. ROM modding is an extensive topic and isn't covered in the guide. Repacking the Unity AssetBundles is also not covered. If you're interested in the latter though, you can look at a tool called UABEA[github.com] to see if you can figure it out. Note that you may have to modify UnityPlayer.dll so that it doesn't perform hash checks if you intend on using those repackaged bundles in Collection of SaGa.

In order to extract these assets, we'll be using a tool called AssetStudio by Perfare. Download the latest ZIP archive release on GitHub[github.com]. Next, extract the archive to a folder and run the AssetStudioGUI.exe file. You should be brought to a screen like this:


Next, you'll want to open the Collection of SaGa local files. Right click the game in Steam, select Manage, then "Browse local files". From here, navigate to this subfolder:


You should now see the following window:


Go ahead and drag the romffl1_assets_all_e8aea7590909c1eb45f3809e4f3da68f.bundle file into AssetStudio. Navigate to the Asset List tab, click FFL1, then select Export, then "selected assets".


This will produce a file called FFL1.bytes. This is actually the Final Fantasy I Gameboy ROM which you can run in an emulator to verify. You can also check out some of the other bundles to see what assets they contain.

Here's a basic overview of what I found:

• romffl1... The English Final Fantasy I ROM
  
• romffl2... The English Final Fantasy II ROM
  
• romffl3... The English Final Fantasy III ROM
  
• romjsg1... The Japanese SaGa I ROM, music, and sound effects
  
• romjsg2... The Japanese SaGa II ROM, music, and sound effects
  
• romjsg3... The Japanese SaGa III ROM, music, and sound effects
  
• menusound... Menu sound effects and background music
  
• ui_assets... UI behavior, animations, textures, and sprites. This one is big, you'll want to filter by type to see them easier.
  
• switch_assets.... Sprites for Nintendo Switch controller buttons. Regular controller button sprites are found in the ui_assets bundle.
  
• vpad_assets... Sprites and behaviors for virtual touch pad buttons.
  
• message_assets... All of the text you can see in the menu system.
  
• credit_assets... Some credit and license text.
  
• defaultlocalgroup_unitybuiltinshaders... Seems to be a shader reference file of some kind.
  
• wallpaperl001 through wallpaperl008... Landscape wallpapers and bounding box sprites / textures as well as behaviors.
  
• wallpaperp001 through wallpaperp008... Portrait wallpapers and bounding box sprites / textures as well as behaviors.

As mentioned in my introduction, the next step would be to attempt rebundling your mod. Admittedly, I don't have much experience with this but I hope my guide was a helpful starting point. UABEA[github.com] seems to be a useful tool for rebundling. As far as I can tell though, UnityPlayer.dll in the local game files needs to be modded so that it doesn't perform hash sum checks in order for these repackaged bundles to work.

Another cool tool that I found is BepInEx[github.com] which seems to be some kind of Unity plugin loader for making in-memory patches. This is more advanced and I'm not at all familiar with this, but they have a plugin developer guide if you're so keen.