DnSpy is a C#/Visual Basic/MSIL decompiler, able to edit compiled versions of games written in those languages. The original creator of dnSpy ceased development, but it is being maintained under the new repository dnSpyEx, which holds improved functionality and is more secure. Cryptark is a 32-bit game, so it is recommended to download the 32-bit version of dnSpy. However, the 64-bit version of dnSpy should work just as well.

Go to the link https://github.com/dnSpyEx/dnSpy/releases/tag/v6.4.1, and download either the 32-bit or 64-bit version of dnSpy. Do not download the .netframework or Source Code zips. Extract the zip once complete.

Open dnSpy.exe. Then, go to the game's directory and drag the game's executable "Cryptark.exe" into the section entitled "Assembly Explorer" in dnSpy. This should automatically populate with every referenced .dll.

Unfortunately, the game has a strange way of integrating with the steamworks API. In order to get C# function references (required to be able to compile the changes we are going to make), you must use merge the Steamworks-CS.dll with the Cryptark assembly. To do this, right-click Cryptark in the Assembly Explorer window. Click the button entitled "Merge with Assembly...", and select from your game's install folder the file entitled "Steamworks-CS.dll". You must then save the module, either by clicking the floppy disc image at the top, or going to "File" and pressing "Save Module". A standard Ctrl+S will not work here.

This is the tricky part. Small mistakes in this section will cause issues, so make sure to follow these instructions carefully.

First, expand the "Medusa" namespace. It should be around the 7th item down the list under Cryptark.exe in the Assembly Explorer.

Navigate to the "Program" script. Within the "using" statement's curly brackets, before the function call "start.Run();", right click on the empty space, and click "Edit Method (C#)...". write the following function call:
Steamworks.Steam.Initialize();
Then, click "Compile" in the bottom right.

You're half-way done! This edit was required in order to ensure that the steam API is initialized. Otherwise, the next edit would cause illegal memory access errors, and the game would immediately crash upon obtaining any achievements.

This next edit is a bit more complicated. Go the the "ScreenManager" script, and scroll down to line ~298, where it says "string achiID = artifactClass.AchiID;". Right click the empty space, and again click "Edit Method (C#)...". After the aforementioned line, write the following four lines:
if (!Steamworks.Steam.Stats.HasEarnedAchievement(achiID))
{
Steamworks.Steam.Stats.SetAchievement(achiID);
}
Don't worry about indentation, C# is a compiled language with end-of-line markers, so it is purely aesthetic. Click "Compile" in the bottom right again.

Now save the file, but not how you normally would; because each script is an individual file, using Ctrl+S will save the individual script you have open. Instead, either click the floppy disc sprite towards the top of the screen, or click File in the top left, and then click "Save Module", clicking "OK" when the window pops up. Ignore any settings therein, or any errors after pressing the OK button.

• It is important to follow the placement of code exactly. Any deviation could lead to errors or unintended circumstances.
  
• You will only earn achievements on steam AFTER closing the game. Changing this behavior would require more code, which'd only make the guide more complicated.