Tome of the Lumiran Archmage:

Whenever the wielder creates a spell, it may be stored in this artifact in an empty slot or in place of another spell. Doing so prevents the spell from being revealed. Every age, for every spell in the book, there is a 10% chance 1d2 spells get revealed. The wielder of this artifact can cast spells from this book 2 mana cheaper and gets a +2 to contestment checks. The book can store 5 spells. 1. Elisho’s Absolute Dispel 2. 3. 4. 5. When the wielder of this artifact dispels a spell it forces a magical malfunction.