Gravenhollow

Gravenhollow was a legendary library located somewhere in the Underdark. Its location constantly shifted throughout the plane by means unknown. Three Librarians tended to the archives—Ulthar, Keeper of the Past, Urmas, Keeper of the Present, and Ustova, Keeper of the Future. The library's knowledge was inscribed on crystal cylinders and tablets that visitors could read. Additionally, a Stonespeaker could be used to induce visions of the past, present, or future.

The tunnel entrance to Gravenhollow.

Visitors to Gravenhollow were lodged at the Gravenhollow Lodge, whose reasonably-priced accommodations supernaturally attuned themselves to the every whim of the business traveler.