The prayer commonly known as Castle of Water protects the caster by creating a physical barrier of water kami to obstruct attackers. The Castle of Air, by contrast, protects the caster by creating a cunning illusion that confuses and bewilders attackers. The Air kami create a circular barrier of false sounds and images, making it incredibly difficult for attackers to actually perceive the correct location of anyone within the bounds of the Castle of Air. An attacker may believe he is striking at the caster when he is actually swinging at empty space.
The circular barrier of illusions is centered on the caster. Once cast, it remains in place regardless of whether or where the caster moves. The illusions can only be fully perceived by those who were outside of the Castle of Air when it was cast; those within the Castle when it appears can easily perceive the shadowy, insubstantial nature of the illusions. If foes from outside the Castle attempt to attack those within it, the illusions will try to misdirect or fool them. Mechanically, such attackers must make a Contested Roll of their Perception against the Caster's Air each time they try to attack someone within the Castle. A success means they manage to briefly see through the illusion and may attack normally for that Round (only). A failure means the illusion tricks them and they suffer a -5k0 penalty to their attack rolls that Round. The illusions cannot affect enemy spells, since the Air kami cannot fool other kami.