You rmaster of magic allows you to prepare certain spells even without access to a spellbook.
Prerequisites
Wizard level 1st.
Benefit
Each time you take this feat, choose a number of spells equal to your Intelligence modifier that you already know. From that point on, you can prepare these spells without referring to a spellbook.
Normal
Without this feat, you must use a spellbook to prepare all your spells, except read magic.