Prerequisites: Fighter, Ranger or Dexterity Score of 15 or Higher

This book contains a large collection of moving annotated sketches depicting optimal fighting styles when wielding two weapons as written by legendary master of the twin blades, Treyavor
If you spend 48 hours over a period of 6 days or fewer studying the book's contents and practicing its guidelines, when you roll a critical hit on an attack roll and use the two weapon fighting bonus action you may roll an additional damage die for the second attack and add it to the total damage. The manual then loses its magic and is destroyed.

Additionally if you have the Two Weapon Fighting fighting style or a feat like Dual Wielder that enhances fighting with two weapons, you may add your proficiency bonus to the damage roll of the two weapon fighting attack.

Notes: Buff