Note: This procedure involves editing a game file; create a backup copy of the file before proceeding. Using a text editor, edit the "rtkrondor.ini" file in the game directory and add the following lines:
Load the game and press [Alt] + C when the final navigation screen appears. The console prompt with a green dollar sign will appear. Then, type "pyromania" followed by [Enter]. Press [Alt] + C again to close the console prompt. Now Mages can cast any spell without cost.