Also called Manor (館, Guǎn in Chinese?), it is China's equivalent of the Mage's Association in the World of Magecraft. While the Clock Tower is the most powerful magus organization in the world, the Spiral Manor may have more total members. The other Philosophy Magecraft organization in China is the Summit Court.
The Spiral Manor and Mage's Association have a feigned nonagression pact with each other.
- The Adventures of Lord El-Melloi II Volume 1: The Man Who Devoured God - Prologue
- The Adventures of Lord El-Melloi II Volume 1: The Man Who Devoured God - Chapter 3
- The Adventures of Lord El-Melloi II Volume 1: The Man Who Devoured God - Chapter 4
 Fate/side material - Encyclopedia: The Mage's Association [Organization name], p.073 [T]
The Mage's Association [Organization name]
An organization created to protect those who seek to learn sorcery, regardless of nationality or field of study. (On paper, anyway.)
Their mission is the management, concealment, and advancement of sorcery.
In order to protect themselves from that which would threaten them (be it the Church, rival organizations of magi, or the monstrosities that punish humans who break taboos), they accumulated military might.
In order to further the advancement (degeneration) of sorcery, they built research facilities.
And, in order to deter crimes committed with sorcery, they created laws.
Their headquarters is located in London, and goes by the unofficial name of "The Clock Tower".
It seems that in the beginning the Association was divided into three great branches, including the original associations that predate the Clock Tower. That is, the "Giant's Pit" of Egypt, and a cluster of associations based in northern Europe called the "Sea of Estray". However, ever since the Clock Tower became the headquarters, mingling between the branches has been on the decline.
Also, they are fundamentally incompatible with the sorcery foundation of the Middle East and the ideological sorcery of mainland China, and the three groups are currently feigning nonaggression.