Forbidden tome

Cost: 15 gp
Weight: 3 lb.

A forbidden tome has a heavy cover and binding, with a lock to keep it closed to prying eyes.

Deadly (You gain a +1 bonus to damage rolls made with a deadly implement. The bonus increases to +2 at 11th level and +3 at 21st level.).
Unstoppable (You gain a +1 bonus to attack rolls against Fortitude when attacking with an unstoppable implement.).

Tome (Most tomes contain one or more wizard spells, often supplemented by information on improving the spells’ effectiveness. You can’t make melee attacks with a tome.
If you are a member of a class that can wield a tome as an implement, you can add the tome’s enhancement bonus to the attack rolls and the damage rolls of implement powers from that class that you use through the tome, and you can use its properties and powers. Members of other classes gain no benefit from wielding a tome.

Published in Player's Handbook 3, page(s) 195, Mordenkainen's Magnificent Emporium, page(s) 40.