most of the hand-written book is about how to construct a large and powerful magical apparatus to capture a hiver without harm to the user , but on the very last page dr bustle writes , or wrote : according to the ancient and famous volume jr.es centum et una quas magus facere totest [ *'one hundred and one things a wizard can do ' ] hivers are a type of demon ( indeed , professor poledread classifies them as such in j spy demons , and cuvee gives them a section under 'wandering spirits ' in liber immanis monstrorum [ the monster book of monsters ] .