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Using a Custom Gamesys

:T1: :T2: :SS2:

NOTEME This is meant not as a standalone tutorial, but something to link to whenever some set of instructions includes telling the reader to use of a custom gamesys. It saves having to repeatedly type the same set of instructions.

Saving the Gamesys

From the File menu, select Save Gamesys. The new filename is up to you, but it is recommended that it’s not too similar to the name of the .mis file, otherwise the you could easily get the two confused. That would be very bad. Save the file into your FM’s working root folder. Once the gamesys has been successfully saved, the status bar should look like this:
Saved Gamesys
On the left is the most recently saved file, and the next item is the currently associated gamesys.

Even if your mission already uses a custom gamesys, it is best to save as a new gamesys anyway, because then you’ll have a working backup.

Associating the Gamesys with your Mission

In the command box, type the command set_gamesys custom.gam (replace custom.gam with your own gamesys name). The status bar should then read:
Gamesys Assigned

Now all you need to do is save the .mis file, so from the File menu, select Save Mission. It is best to save it as a new .mis file and so that you can use the previous one if things go wrong. After that, the status bar should then read:
Saved Mission

To ensure that everything has worked, reload the mission. You can then check that the changes have been remembered (e.g. new textures have sounds, new archetypes are in the hierarchy etc).

Saving Over the Current Gamesys

If your mission already uses a custom gamesys and you just want to save over it, select Save Gamesys, and select the .gam file. It is then recommended that you then save your mission, remembering not to overwrite the .gam file.

A Warning

If you save your gamesys, and then go to save your mission, the .gam file will still be selected in the Save window. If you do not notice, and you click on Save, the .gam file will be overwritten with the content of your mission. If you load a mission which requires that .gam, you will receive an error message about failing to inherit from a non-inheritable archetype.

Automatic Backups

Whenever Dromed saves a file, it creates a backup of the old file. So if you immediately notice that you forgot to rename the file before saving, you can still recover the old gamesys or mission.

The backup when you save a mission is backup.mis. Saving a gamesys will create a file named backup.gam. And, of course, there is backup.cow for cow files. (Which are explained next.) If you accidentally save a mission using the name of a gamesys, you should first rename the newly saved file to its proper name.

  custom.gam → miss22.mis

Then you can rename the backup, which has the extension .mis but is really a .gam.

  backup.mis → custom.gam

Your files should now be in order. As long as you hadn’t tried saving anything else in Dromed.

An Alternative: The .cow File

An alternative to saving a .gam and .mis file is to save in the .cow format. This type of file is a combination of the mission and the gamesys. From the File menu, select Save Cow. The second item in the status bar will still refer to a .gam file, but the mission will not be using it.

NOTEME A .cow file can only be used by Dromed. When you want to make the mission playable through Thief, you have to split it up into its .mis and .gam components.

Converting .cow to .mis and .gam

  • Load the .cow in Dromed, and select Save Gamesys.
  • Choose a suitable name (e.g. mission_name.gam), and save the file in your Thief installation folder
  • Type the command set_gamesys mission_name.gam.
  • Select Save Mission, and remember that the file needs a name like missXX.mis, where XX is a number.

Which is Better?

Each method has it’s good and bad points:


.mis and .gam

  • In this format the mission can be played/tested in Thief simply be renaming the .mis file (and configuring missflag.str).
  • The gamesys can easily be shared by several missions. Each time you change it, other missions will immediately have access to those changes.


  • With a single format, you are less likely to make a mistake and save the mission over the gamesys.
  • During editing you have just a single file to worry about. This can help you keep your folders organised.


.mis and .gam

  • If you are frequently making changes to your mission and to the gamesys, you might save the .mis over the .gam, thus losing the gamesys.


  • You might accidentally select Save Mission but then overwrite the .cow file, which would effectively revert the mission to dark.gam. The big problem with this is that you would get no error messages, so you could have made many changes to the mission before realising your mistake.
dromed/gamesys.txt · Last modified: 2020/09/18 15:48 by r_soul