Atlas Institute

One of the three major branches of the Association. Located in the Atlas mountains of Egypt, it is a place where those dedicated to the study of alchemy gather.
Unlike the modern alchemy that rose to prominence in the middle ages, the alchemy studied by Atlas could be said to be the progenitor of magecraft, and an attempt to unravel the truth of the world.
For some reason they are on extraordinarily bad terms with the Prague Association, and even the Clock Tower, the very heart of the Association, keeps their distance. They are colloquially known as the Giant's Pit.
In order to avoid the “end” proven by their first director, they endlessly create and dispose of weapon after weapon.
There is a saying in the Prague Association: “Lift not the seal of Atlas, lest ye destroy the world seven times over.”
…The reason being that the weapons created there to save the world are ultimately nothing more than tools that will further its destruction.
Though calling it “one of the three major branches of the Association” sounds nice, in reality it is more like an independent think tank. They have been known, on rare occasions, to loan out their alchemists to other mage's associations and even the Holy Church upon request.
In order to hire an Atlas alchemist, however, one of the written contracts issued by the Atlas Institute is required. Only seven of these contracts were ever issued, and the Atlas Institute considers their recovery a top priority.

Tsukihime Dokuhon Plus Period: Tsukihime Dictionary Revised
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The institute Sion belonged to, and one of the three major branches of the Association. Located in the Atlas mountains of Egypt, it is a place where those dedicated to the study of alchemy gather. Colloquially known as the Giant's Pit.
Unlike the modern alchemy that rose to prominence in the middle ages, the alchemy studied by Atlas could be said to be the progenitor of magecraft. For some reason they are on extraordinarily bad terms with the Prague Association, and even the Clock Tower, the very heart of the Association, keeps their distance.
In order to avoid the “end” proven by their first director, they endlessly create and dispose of weapon after weapon.
There is a saying in the Prague Association: “Lift not the seal of Atlas, lest ye destroy the world seven times over.”
…The reason being that the weapons created there to save the world are ultimately nothing more than tools that will further its destruction.

MB Act Cadenza PS2 Manual: Tsukihime Dictionary