Black Scrolls of Rassilon

The  were a set of scrolls containing forbidden knowledge from the Dark Time. Although to the Fifth Doctor once quipped that the Black Scrolls were "out of print" by his time, they appeared to be unique artefacts rather than widely-reproduced texts. The Scrolls were held within a casket marked with the Seal of Rassilon (TV: The Five Doctors)

History
According to one Time Lord historian, the Black Scrolls were originally written as a set of instruction for the use of the Time Scoop, which Rassilon wrote and hid in the Capitol alongside the Time Scoop itself after he officially banned the device's used. The historian speculated that Rassilon meant for his successors as Presidents of the High Council would be able to find and use the Scoop, albeit for more practical purposes than the Games in the Death Zone. (PROSE: A Brief History of Time Lords)

Indeed, the Scrolls were found by President Borusa (TV: The Five Doctors) thanks to the help of Jelpax, who was an expert in early Gallifreyan artefacts. (PROSE: Divided Loyalties) To falsely implicate Jerricho in opening the Death Zone, Borusa left the casket and the scrolls (or convincing copies) in his chambers. Before anyone could examine the scrolls to confirm what they were, Borusa ensured that they spontaneously combusted. (TV: The Five Doctors)

At one point, however, 's TARDIS library contained the Black Scrolls, alongside other reviled works such as the Insidium of Astrolabus. (PROSE: The Quantum Archangel)

In preparation for the mass production of the Cwejen, the Superiors' occultists used the surviving "black scrolls" to invoke the aid of entities whose existence could not be publicly acknowledged. (PROSE: The Ursine Brood)

Before Gallifrey was destroyed (PROSE: The Guide to the Dark Times) by, (TV: Spyfall) River Song visited the planet to steal the Black Scrolls. Hence, the stories of the Dark Times were preserved beyond the Time Lords themselves. River and her wife used the Scrolls as the basis of The Dark Times Times. (PROSE: The Guide to the Dark Times)

Behind the scenes

 * The word The is indicated to be part of the title in The Quantum Archangel.

Pergaminhos Negros de Rassilon