An oversight with the Lunar Grimoire

There's an oversight with the Lunar Grimoire. Using the book to summon a full moon changes the moon cycle, changing the day of a new moon. If a player were to use it up to every 9 days (which isn't that difficult since the book is cheap) the shadow pieces fight would be impossible to do. An easy fix to this would be to either make the full moon not change the moon cycle and not work on days with a new moon, or to add a book that sets the moon phase to a new moon.