Light Knives

Step 1: Find your spark
The term 'unlock' is generally avoided due to connotations- everyone has a spark, and it's not bound behind any particular ritual. It's simply the first step in self-discovery. For example, there are plenty of smiths who augment their work using their spark, despite lacking any sort of formal magical training. It's slightly easier for a native to the region to do so than the average human, but this is only statistically relevant across populations. Locking somebody in a dark room would theoretically be a good way to unlock a spark by playing on the instinctual desire to see, but the region is cursed to spawn monsters in darkness, so the method isn't actually safe.
Step 2: Throw knives
What? You've shown the instructor that you can make light, and now they're telling you to throw knives at a target? What does this have to do with anything? They refuse to explain any further. You've got to throw in a specific motion, too- one that really doesn't feel like the best way to throw a knife.
Step 2.5: Throw even more knives
There's a reason mages always seem to win at darts when spotted in southern taverns. By the same token, they tend to be surprisingly bad at knife-throwing.
Step 3: There is no knife
Maybe you're practicing and reach for a knife that isn't there. Maybe somebody pulls it out of your hand without you noticing. Maybe you just feel yourself going through the motions, despite not having a knife in hand. Except, now you have one. There's a reason mages are never considered truly unarmed: strip away their implements and they can still, at the very least, summon a blade.
The reasons behind it being a knife, despite the technique being more applicable to darts, has two main reasons: tradition, and practicality. Knives are useful- not just for combat, but for preparing food, marking surroundings, and cutting rope. What're you going to do with a dart? The thing is, the knife throwing technique is a really bad way to throw physical knives, but very well-optimized for light-based ones due to how physics affects them differently.
Step 4: Abstraction
You have become aware of the feeling required to summon hard light; the twist in the soul to make will into reality. Start using the feeling without the crutch of physical motion, and you can materialize your knife with a thought.
Step 5: Adjustment
Now you know how to create through pure will. Start adjusting what you make- learn to bridge the gap between visualization and materialization. Materializing simple shapes like spheres and cubes doesn't take much finesse, but it's quite taxing. Adjusting your image of a knife, on the other hand, takes little effort because of your experience with the shape- however, it's a much trickier process requiring more conscious thought. Your mind is, quite literally, a muscle here.
Single-cast swords may be inefficient as practical spells, but this doesn't stop basically everyone from trying to make one the first time they're told to adjust their projections.
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Light knives are one of the standardized spells taught to mages- typically, the very first. One materializes a hard light bladed object out of hard light and throws it at the target. Note that the nature of hard light means that the user is at no danger of cutting themselves.
The typical mnemonic device used is to set one's arm in a position ready to flick forwards and throw the knife, for obvious practicality reasons.
Theoretically, blades are the ideal weapon to create from hard light for human combat: force applied to the blade can be minimized while still having a cutting effect by having it be thinner, only limited by the user's conceptualization of sharpness.
The overall thickness is mostly limited by one's idea of how thick a blade can feasibly be while maintaining strength (as visual dissonance is one of the key sources of inefficient hard light projection). As a result, typical beginners have relatively thick blades, which trend towards becoming infinitesimally thin as they practice. This extends the blade's range and speed due to reduced air resistance.
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A common fallacy from non-mages is that a simpler object is easier to materialize, so why not start teaching hard light by making a sphere? This is incorrect because simplicity is only one factor- a simpler object is indeed easier to visualize. However, humans think around tools, and to think of an abstract sphere floating in space is not intuitive. Therefore, one would effectively have to play basketball or something similar in order to conceptualize spheres, at which point knives are a simply more practical use. Someone who extensively skipped stones as a child may have an easier time materializing a flat rock, for example. Some believe that 'light knives' actually originated as 'light rocks'; and as Hauntfall grew as an institution, they made the switch for more consistency and to create a more refined image.
Light knives are generally used as the very first true projection spell taught. Projection prodigies often replicate this effect in childhood with other objects, requiring far less repetition to engrain the expectation. These tend to be varying degrees of useful: Vid's first projection was a hard light comb, for example. Seeing as hard light projections cannot affect one's own body, this was literally useless.