Vellum Citadel is a location in Tyranny.
The Vellum Citadel was a library fortress, the largest archive of the written word in the Tiers. The School of Ink and Quill protected and maintained the archive of ancient lore for centuries, standing apart from the political upheavals of the Younger Realms as an enduring pillar of knowledge and culture.
The Sages of the Vellum Citadel publically swore fealty to Kyros, but from within the safety of their Vellum Citadel, these scholars continued to study and copy forbidden lore, and used magic to repulse any attempts by the Disfavored and Scarlet Chorus to claim the Citadel that was promised to the Overlord.
In retribution, Kyros pronounced an Edict of Fire on the Vellum Citadel, turning the home of the School of Ink and Quill into a smoldering ruin now known as the Burning Library.