Bibliotheca Basileus

is the Noble Phantasm of Ptolemy I Soter in his form as the Pharaoh of Egypt.
The Throne of Heroes recorded Ptolemy and the Library of Alexandria as one entity, and this Noble Phantasm is the manifestation of them being one and the same. He has access to all of the library's knowledge and mechanisms.
For example, because Ptolemy and the Library of Alexandria are one and the same, the mirror located on Ptolemy's person is therefore the same as the large mirror that the library used to start a volcanic eruption during the events of The Adventures of Lord El-Melloi II, and so Ptolemy's mirror could fire a magma-hot beam of light. Ptolemy is able to control all aspects of the library, such as closing it off from outsiders, freely controlling the space distortions used to quickly move around inside the complex, and condensing information from the library into crystals for the knowledge to be shared.The Adventures of Lord El-Melloi II Volume 5: Legacy of the Alchemist (Lower) - Chapter 5
In Fate/Grand Order, while this Noble Phantasm summons the "surface" Library of Alexandria which he created with his son, Ptolemy can utilize and fuse his Library with the "other" Library of Alexandria from his colleagues of the Atlas Institute.Fate/Grand Order - Ptolemy (Archer) Profile - Translated by PkFreezeAlpha
Photonic crystals akin to Philosopher's Stones are created en masse, gifts born through the wisdom of all Atlas Institute members, and act as a defense mechanism while striking the enemy. With the wisdom of the Atlas Institute, Thought Acceleration and Memory Partition are both granted and strengthened. This is the same kind of future-focused thinking that the alchemists of the Atlas Institute all possess.
The information stored within the Noble Phantasm's library is updated to the modern day, similar to how the weapons inside Gate of Babylon are updated. For example, when summoned during the events of Fate/Grand Order Ptolemy reads a book from the library which tells him about the events of the Observer on Timeless Temple arc.Fate/Grand Order - Event: Castle of White Sky, Castle of Black Night - Chapter 12 It even has profiles of individual people, such as Lord El-Melloi II and Reines El-Melloi Archisorte.Fate/Grand Order Ptolemy (Old) Lines translated by Reddit User PkFreezeAlpha.
==References==
Category:Noble Phantasms
Category:Conceptual Noble Phantasms
Category:A+ rank Noble Phantasms
Category:Barrier Noble Phantasms
Category:Anti-Army Noble Phantasms
Category:Noble Phantasms introduced in Lord El-Melloi II
Category:Noble Phantasms of the Ionioi Hetairoi