The Book of Tempus is an extremely old book written in Latin. The exact age of the book is unknown as it is well-preserved, even the natural occurance of mold forming within the pages not having transpired. The book contains pages and pages that apparently teach the reader how to make items capable of manipulating time.
The book itself appears to contain no powers of its own, but within its pages are extremely long and detailed rituals that can teach a person who to make an item capable of manipulating time. Various examples are detailed within, including a paintbrush, a lyre, a staff or cane, a sundial and an hourglass. The Tempus Clock was one such item made from the book, requiring months of work to make possible.