The GM is perfectly within rights to restrict sorcery to an approved grimoire for the campaign, declaring that only these spells can be learned or improvised. If he does allow sorcer ers to improvise completely new spells, each such improvisa tion must make sense as a new, general spell for the setting. The key word here is “general”; the GM should shut down overly specific spells.
В советах по созданию заклинаний есть тоже лимиты, вроде Area на 9 странице.