Leaving this here for anyone else who needs it in the future as well. When you download Empyrean, in the main folder there should be a folder titled 'Mods' or something similar. Using Notepad (or TextEdit if you're using Mac), create a new file with a single line:
$DEBUG = true
exactly as written. Save it as a ruby file, (I used 000_debug_mode.rb). Make sure it saves as .rb and not .txt. Drag it directly into the Mods folder. If you boot it up, and it skips the title screen, that's a good sign that it worked. Once the game is loaded, pressing F9 should bring up the debug menu.
Edited to add the premade file for anyone confused by the instructions. This will work for most fan games, you just may have to figure out exactly where to put it in others.
000_debug_mode.rb
