A tome of understanding was an arcane book that contained magically-infused texts, written to increase the reader's common sense and wisdom. The writings inside contained exercises designed to improve the reader's intuition and insight, though topics and themes of these tomes varied. They could contain scholarly treatises and accounts of legal, philosophical, and arcane subjects, or mental exercises that encouraged new modes of thinking.
If the reader completed the book within a period of 6 days, they were endowed with a great improvement to their intuitive and reasoning capacities, potentially transcending their natural potential. This magic would transfer from the tome to the reader, causing it to become non-magical.