Manual of Quickness of Action

D&D 2014 item: Manual of Quickness of Action. Source: Dungeon Master's Guide (2014). type Wondrous Item, Very Rare rarity This book contains coordination and balance exercises, and its words are charged with magic. If you spend 48 hours over a period of 6 days or fewer studying the book's contents and practicing its guidelines, your Dexterity score increases by 2, as does your maximum for that score. The manual then loses its magic, but regains it in a century. Wondrous Item Very Rare

Source: Dungeon Master's Guide (2014), p. 181 - Licenses and attribution