Shielding Winds, Wind School, Level VII
Shielding Winds is an advanced defensive Wind spell, similar to but more powerful and versatile than the simpler Insubstantial Shield spell. Its main purpose is likewise to deflect ranged attacks, mundane or magical. However, instead of defending against attacks from all directions as Insubstantial Shield does, its effects are typically focused in a small region, creating a much stronger defense from projectiles coming from that direction, but leaving the mage open to any potential attacks from elsewhere. Magi who are more powerful would be able to cover a larger area with the spell without weakening its effect, literally erecting a wall of wind between themselves and their attackers. With enough skill, it is even possible to extend the affected region such that it completely surrounds oneself, negating the main disadvantage of this spell compared to Insubstantial Shield.
Spell Effect
An object's car'all is not separate from its surroundings, and thus is influenced by the elements in its surroundings. A projectile in flight is completely surrounded by air, which consists of mainly of Wind ounia, thus allowing a Wind mage some measure of control over it. I love this point, it should be in a quote collection on magic.
The spell draws Wind ounia into the target region From whence?, creating a region of air where the influence of Wind is much greater than usual. This is further enhanced by the caster, who will also emphasise the influence of Wind's property of movement, as well as define a direction of movement. A projectile entering the target region will come under unusually strong Wind influence, especially with regard to its movement. This causes it to be deflected off its original course and into one which, assuming the caster is relatively competent, should miss the caster.
Simply put, the spell generates a region of strong wind that knocks aside projectiles entering it.
I would like to hear a bit about the strength of this wind. What projectiles can we expect to turn away at what levels?
Casting Procedure
In an actual combat situation, one would most likely have very little time to react to a ranged attack of the nature the spell is meant to defend against. Thus, the usual procedure is to first set the air in the target region into motion, by increasing the influence of Wind and the property of movement in particular. This is not very different from casting Conjure Wind, though in this case most magi prefer have the wind take a circular path, like with Insubstantial Shield. The time required to do so should be almost negligible, and while the winds conjured at this stage is not as strong as they will be when the casting is done, they do provide some defense. Then, while sustaining the effect, the mage draws Wind ounia from the surroundings into the target region as quickly as possible, boosting its strength.
It would be nice to have some speculation as to the effects of drawing WInd ounia from the surroundings, and the eventual side-effects of that. Specifically, I wonder if that creates a "hole" (think pressure) that causes air to rush into it, thus creating wind as a side-effect. This side-effect could, with some skill, be used as a boost, to quickly create a strong gale of wind. What do you think?
The more risky way, which some favour, is basically the reverse of what is outlined above. Wind ounia is first drawn into the target region, which, due to the increased Wind influence, could also result in wind being generated. The mage then strengthens the wind, or conjure it in the unlikely event of there being no wind present, and takes control of it. I wonder, of course, depending on the above, whether drawing passive ounia in (ounia that do not express movement) will make wind all by itself. You would need to "activate" them, no?
Magical Formula
Not yet defined
Target
The target is a region of air between the mage and the projectile or projectiles the mage is to be defended against. Initially, a mage would normally learn to affect a more or less circular region about two peds across. As one grows stronger, one would be able to affect a larger region, and with enough skill, regions of different shapes, which might be more useful in some situations. Completely surrounding oneself with the spell effect, as previously mentioned, is one such possibility.
Reagents
<insert reagent here> is the reagent most commonly used for this spell. However, one usually learns quite quickly to cast it without the aid of a reagent, so as to minimise the casting time. I would suggest the obvious, feathers of some kind.
Magical School
Wind School, Level VII
Spell Class
Physical Representation of Sphere III
Range
It is not inconceivable for a mage to be able to create the effect a great distance away, assuming he or she is sufficiently powerful. Usually though, it is cast no more than an arm's length away from the mage. Some estimates on maximum range?
Casting Time:
The effect should manifest almost instantly once the mage commences the casting of the spell. It will take a few blinks to reach full strength however.
Duration
Despite being a Sphere III spell, Shielding Winds is largely based on Sphere I principles, and has the similar limitation of having to be constantly sustained by the caster. The duration is thus however long the caster can sustain it, which for a mage at Level VII should be a minute or two, or much longer if one does not mind complete exhaustion. It is however not necessary to sustain the spell for more than a few blinks in most cases.
Countermeasures/Enhancing Measures
It is generally advisable to not be in a situation where one has to use this spell in the first place. If one nonetheless ends up in such a situation, there are a few things one can do to improve one's chances of survival.
First, if one expects to have to have to use this spell, one could have the reagent in hand and ready for use whenever it might be needed. The use of a reagent of course helps one to cast better. It can be quite troublesome to hold the reagent for too long however. Learning to react very quickly is helpful too, and not only for this spell. With regard to the use of this spell though, a quick reaction means being a lot more likely to have the spell up before the projectile reaches the target. The alternative would be to cast the spell first, then wait for the attack, which requires rather more energy. And, of course, the further away one is from the attacker, the more time there will be to react, so one should endeavour to be as far away from the attacker as possible, if not, as mentioned earlier, in an unassailable position.
To get around such a defense without the use of magic, attacking from several directions simultaneously has a relatively good chance of working. For magi who cast the spell in anticipation of an attack, withholding the attack is a good tactic if one is in no hurry. Trying to catch the mage off-guard could also work.
For magi, the above also apply, but there are many other possibilities as well, depending on one's element. Spells could be used to distract the mage and prevent him or her from getting the spell up in time, or to break the caster's concentration and end the spell, hopefully at the right time to let an attack through. There are also spells that can directly injure the target instead of producing a projectile to do so.
Nice last section, we often have next to nothing in here.

Oh, finally, a note on spelling: You confuse "Its" and "It's" in a couple of places.