The answer is: delete the save files! New question: Where do I find these files?
Save File Locations
How can I delete my save completely?
If you really wish to completely restart your game, you need to delete all your save files present in:
- C:\Users%UserName%\AppData\LocalLow\Ishtar Games\The Last Spell
You will also need to deactivate Steam Cloud. Be careful, all your progress in the meta etc… will be lost.