1. Edit RTKRONDOR.INI and make sure the following lines are in it:
[Console]
Console=1

2. After the game reaches its final navigation screen, press ALT-C to bring up the console prompt (the green $ sign).

3. Type "PYROMANIA" (no quotes).

4. Press ENTER and ALT-C to remove console prompt.

The cheat enables your mages all spells and makes your mages cast it without cost! Unfortunately the provider of the cheat says that this is the only useful cheat that made it into final game.