very rare
Tome of Clear Thought
Wondrous item, very rare
This book contains memory and logic 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 Intelligence increases by 2, to a maximum of 30. The manual then loses its magic but regains it in a century.
Tome of Clear Thought is from the System Reference Document 5.2.1 (“SRD 5.2.1”) by Wizards of the Coast LLC, used under the Creative Commons Attribution 4.0 International License. Full attribution is on the Licenses & Attribution page.