The Worshipful and Ancient Law of Gallifrey

The Worshipful and Ancient Law of Gallifrey was a book that was once stored in the Panopticon Archive on Gallifrey. It was also the 'key' to Shada, the Time Lord's prison planet. When the pages were turned inside a TARDIS, it would take the craft to Shada. (DW: Shada, WC: Shada)

The text of the book was written in ancient Gallifreyan and read largely as gibberish, though the book itself had several remarkable features:
 * It absorbed radiation.
 * It had no discernible atomic structure.
 * Time ran backwards over it.
 * It was impervious to damage.
 * It could not be spectrographically analysed.

Removal from Gallifrey and subsequent use
It was stolen from Gallifrey by Salyavin, who subsequently requested that the Doctor return it to Gallifrey for him. Following this meeting it was stolen by Skagra, who used it and the Doctor's TARDIS to travel to Shada. (DW: Shada, WC: Shada)

Once, the Doctor used a copy of the book to imprison a malevolent psychic entity known as the Garvond. Having done this, he dumped the copy in a dimensional fissure. (NA: The Dimension Riders)