Banner of the West

The Banner of the West (西旗) is a symbolic weapon used in modern Western magic.

Principles
The Banner of the West is a symbol of exorcism, consisting of an equilateral triangle with a cross in the center. It protects the user by monitoring and rejecting evil power approaching their ceremonial grounds (such as something resembling Telesma out to attack humans). It is considered one of the most useful and convenient symbolic weapons in modern Western magic because evil and useless powers are affected while good and useful powers are left alone.

When using the Banner of the West against Coronzon, Aleister Crowley used the following chant: “The Banner of the West. Those dual symbols and color layout will reject evil. I cannot eliminate all doubt from thy nature, so I shall protect thee by severing all ties. Furthermore, I am blameless and need not leave this location, so the evil one must remove herself in accordance with her sin!!” (西旗. 二重に重なる象徴と色彩設計によってかの悪性を拒絶せよ. 我は汝の性から疑義を払拭できず、よって一切の繋がりを断つ事で守りを得る. さらに語れば守りに際し咎なき我がこの場を離れる必要なし、悪たる者はその責により自ら退出するがよい!!)

Coronzon Arc
When Coronzon manage to return from the 'new world' to the shutdown Academy City, Aleister temporarily sealed it with the Banner of the West, using an improvised method of connecting the city's roads to form the symbol, inspired by Karasuma Fran's earlier attempt to rescue Kamisato Kakeru from the 'new world'. This brought some time for Aleister to seek out the measures which Coronzon had placed in the British Commonwealth to prevent its destruction.