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 within a TARDIS it would take the craft to Shada. (DW: Shada, WC: Shada)

The text of the book is written in ancient Gallifreyan and reads largely as gibberish though the book itself has several remarkable features:

It absorbs radiation

It has no atomic structure

Time runs backwards over it

It is impervious to damage

It cannot be spectrographically annalysed

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)