The Book of Tarchamus was a sentient book that was actually the consciousness of the ancient Netherese arcanist Tarchamus the Unyielding. After Tarchamus built his library, he turned his physical form into a powerful mummy with the help of his apprentices. He placed most of his intelligence into a magical tome with the remainder staying with his physical body.
The book could communicate telepathically and read minds. It was willing to share information with researchers in the library but often answered questions with half-truths or outright lies. In 1478 DR, it was removed from the library by the Harper Tam Zawad, who utilized its mind-scrying abilities to interrogate suspected Harper turncoats.
The book appeared as a large tome written in ancient Netherese. The words seemed shift when read and the volume seemed to remain unusually dusty. A page had been cut from the book at one time but was reunited with the book by a party of adventurers led by Tam.