From the introduction: Grimoire uses a heavily Narrative Style, where the Game Master is expected to know the game mechanics while the Players just need to figure out the ins-and-outs of spellcasting. The Players are therefore able to keep focused on whatever terrible activity they’re currently taking part in while the Game Master does all that pesky dice-rolling in private where nobody can see and complain that rules aren’t being followed. Ultimately the Narrative Style is about telling a story using where the participants use the in-universe rules more than anything else. Game mechanics are used until they get in the way, and from there it’s just whatever makes for the best story. There are no strict rules preventing you from trying to do whatever it is you want, so long as you can figure out how to make it happen. The Narrative Style takes to heart the belief that you should never let the rules get in the way of a good story.