Hard Air
The ability to manipulate air molecules in order to create invisible constructs.
Manipulation
By hardening the air around them, the user can create constructs of anything they can imagine and have those constructs act how they believe those constructs should act.
Air
The ability requires air to function.
Requires focus and concentration to maintain the constructs, and a loss of focus can result in the object in question falling apart back into regular air.
As the user's imagination is used to form the shape, if the user cannot think of an object to use, then it becomes impossible to create such object.