Spell Book
Spell book is an object, where heroes store their learned spells. Is is also needed to cast a spell. Any hero can have a spell book, but typically might heroes, like knights or beastmasters, do not have them at the beginning of custom scenarios. However, alchemists and death knights do start with one. Spell books can be bought from a mage guild for 500 
.
A spell book cannot be traded to another hero, nor can it be lost after a defeat.