In your root Impossible Creatures directory, you'll find a folder entitled "RDNTools". Within it lie the most basic tools you will need to start editing IC. Inside, you'll find the following utilities:

This is perhaps the most important of all the RDN modding tools. Primarily, it is used to extract contents from the game's various .SGA archive files, which contain loads of game and mod data, such as editable .LUA scripts and entity blueprint files (.EBP), as well as textures, decals, et cetera. In addition, ModPackager is also capable of packing mods, addons, and map packs into easy-to-use installers without the use of third-party software.* Think of ModPackager as 7-Zip or WinRAR for IC's files.

ObjectEditor is used to create, open, and modify the attributes of .EBP files. For the most part, this tool is only used when creating your own models, which is beyond the scope of this guide, so we won't worry about it much.

This one is pretty self-explanatory. It's essentially just the creature combiner. It's used to see how user-created stock animals will mesh with other creatures before they're loaded into the game. Some mild editing, such as limb-scale adjustment, is also done from within ComboTest.

Used to create effects (FX), such as ranged attacks or splashing water. There are many uses for this tool, and a tutorial can actually be found inside Impossible Creatures\Documents.

Used for converting .MP3 or .WAV audio files into IC's .PAT format. Use this if you have any custom music or sound effects you'd like to add to the game. You'll be able to do some light editing of your audio file before you convert it as well, if you desire. Note: Custom audio unfortunately appears to be broken in the Steam edition.

Used for creating and editing custom menus and other UI screens for IC. This tool requires some additional setup to run properly and will likely be getting its own guide at a later date.

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While not technically part of the RDNTools package, it's still worth a mention here. The Mission Editor is IC's map editor, and is used to create custom maps and campaign missions for IC. The editor can be run either as a launch option when starting IC through Steam or directly from the executable (MissionEditor.exe) in the root IC directory. There is a good bit of documentation located in Impossible Creatures\Documents as well.

A detailed tutorial for the Mission Editor can be found here:
Impossible Creatures – In-Depth Multiplayer Map-making Guide and Advice
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*With the advent of Steam Workshop support for IC, these functions have largely been rendered obsolete.

Now that you've read about all of the modding tools, you're ready to actually begin. Open up ModPackager. You'll be greeted by a mostly gray window with a toolbar at the top. On the toolbar, click "File" and then "Open". Select "Engine.sga". You'll be taken to a white screen with a lot of files and folders. Navigate back up to the toolbar. Select 'Archive" and then "Extract Archive". Make sure you extract the contents to a new folder. It doesn't matter where it goes or what you name it, but I like to name it simply "Engine" and put it in my root IC directory. Wait for the extraction to finish and then close ModPackager. You can now open the folder you created and see all the contents of engine.sga. The various .LUA files you see can be opened and edited in Notepad or Notepad++.

Repeat the above process with ICData.sga and InsectData.sga.

I encourage you to poke around with these files on your own and see what you can find. Have fun!

Once you've extracted all of the .SGA files, you're ready to set up the framework for your mod. Every IC mod requires the following to run, without exception:

• A mod folder
  
• A mod folder in Impossible Creatures\Locale\English (or your desired language)
  
• A .DLL file
  
• A .MODULE file
  
  These items should be placed inside the main Impossible Creatures folder.

Create a new folder within your primary IC directory. Name it whatever you want the title of your mod to be. Inside it, create a folder named "data". This is where the meat of your mod will lie. Everything you extracted from the .SGA files corresponds to its location inside the data folder. For instance, if you've edited the file "tuning.lua" from the folder "sigma" inside ICData.sga, that file will go into Your Mod\Data\Sigma. This applies to every file and folder from the three .SGA files you extracted. In most cases, the only thing that needs to be inside your mod folder is the data folder. However, it's also a good place to put changelogs or credits.

Inside Impossible Creatures\Locale\English*, create another new folder, preferably with the same title as your mod folder. Inside this folder, you need to have the files "modtext.dll" and "modloc.sga". You can simply copy them over from another mod, such as Insect Invasion. Modtext.dll contains all the game text specific to your mod.

To edit it, you'll need to download a resource editor.
I recommend using Resource Hacker. You can download it here: http://www.angusj.com/resourcehacker/

Resource Hacker has since been found to break mods. Use it at your peril.
Please see see this guide for text editing:
Modifying Game Text With Visual Studio (No Resource Hacker)

You'll need to do a little bit of editing in order for your mod to appear in-game. Open your Visual Studio project. Press Ctrl+F and type in the name of the mod you copied the file from (for instance, Insect Invasion). Press enter and you'll be taken to the relevant string. Rename it to the title of your mod. Build the solution and copy your .DLL to IC. That's it for the locale.

To get the .DLL and .MODULE, you'll need to copy them from another mod. We'll use Insect Invasion as the example again. In your root IC directory, find "InsectMod.dll" and "Insect.module". Make copies of them and change both of their names to the title of your mod. Then, open the .MODULE in Notepad. Edit the file so that it looks like the following (where "yourmod" is the title of your mod and "moddesc" is your mod's description. You can change the number for "ModVersion" to whatever you want, but don't leave it blank):

By default, IC searches for content in Impossible Creatures\Data. It only looks for anything inside of a mod folder when it is explicitly told the folder exists. This means that if, for instance, you want to open a creature's .EBP file in ObjectEditor, you will have to copy it to that main data folder first, then copy it back to your mod when you are done editing. However, you can tell IC to search inside your mod folder via the file pipeline.ini, found inside the root IC directory.

When you open the file, you should be greeted with this:


You can simply append your project to the end of the file using the following format:


Now your mod's folder should be accessible from the RDN Tools (with the strange exception of ComboTest—you'll still need to copy files to the main data folder for that one, unfortunately). This step isn't required for your mod to work, but it cuts out a lot of headache.

...And that's it! You're done! If you've followed all of the steps correctly, you should now have a fully functional Impossible Creatures mod.

Have fun tinkering!

Note: To learn how to upload your mod to the Steam Workshop, run IC through your Steam client and select "Launch Impossible Creatures Workshop Manual".