When does it makes sense for Sword Masters to use a sword beam as a one-time killing move?

Question

Intro

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In the creation of my Wuxia-inspired world, 'Sword Intent' is a cornerstone concept where sword masters channel a life force known as 'Qi' to perform extraordinary feats. 'Sword Intent' in my world is not an undefined magic but a force governed by specific principles, akin to a form of energy manipulation. To avoid making 'Sword Intent' an omnipotent plot device, I am looking to establish clear rules for its use and limitations in my world.

Qi

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1. 'Qi' is a finite internal resource, regenerated through rest and meditation.
2. It is stored in the lungs, with an average volume of 6L (6000 cubic centimeters) maintained at a staggering 30PSI.
3. 'Sword Intent' is the mental ability that a practitioner uses to shape this 'Qi' into a sword-like form.
4. 'Qi' shaped by 'Sword Intent' has particle bonds unbreakable by physical means, only broken by other sources of Qi
5. Qi can be compressed to extend range and potential damage.

Practitioners utilize 'Sword Intent' in three forms, Qi Blade, Qi Bullets, and Qi Beams.

Qi Blade

1. The Qi blade is a 1 cm thick coating wrapped around an object.
2. Provides moderate protection against Qi attacks and also cuts through non-Qi materials with impunity.
3. Qi consumption: 200 cubic centimeters per layer, lasts 5 minutes with concentration. 30x

Qi Bullet

1. The Qi bullet gathered in the veins and compressed before being shot out.
2. Shape is 10 cm in length and 2 cm in diameter, flies at 500m/s (musket bullet).
3. Qi consumption: 120 cubic centimeters / 10 metres range. 50x

Qi Beam

1. The Qi beam is a hyper-concentrated beam of Qi at 300PSI kept in shape by sword intent.
2. At 0.25 cm in width, it can reach a maximum range of 24 meters in length.
3. Adjusting the width and concentration of the beam allows a range between 0.5 to 100 meters.
4. Can only be used a limited number of times per day due to physical and mental limitations

Summary

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In summary, Qi has three forms. Blade, bullet, and beam. Qi blade grants sword master unparalleled close combat ability and defense against Qi bullets, Qi bullets are versatile medium range projectiles, and Qi beams are a one-time-use sweeping beam.

Given these limitations, does it make sense for the Sword Masters in my world to use Qi in a Beam form when they have access to Qi blades and Qi bullets?

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Examples to help illustrate:

Sword Master using Qi Beam:

Master Liang stands in the center of the training courtyard, his eyes closed in deep concentration. The air around him shivers as he summons his 'Qi', drawing the finite resource from within. His pupils flicker open, revealing a steely gaze as he extends his palm toward a group of bamboo stalks across the yard. With a sharp exhalation, he channels his 'Qi' into a focused beam twenty meters in length, no wider than a chopstick, and swings it with a flick of his wrist. The 'Qi Beam' slices forth, slicing all the bamboo in the clearing cleanly in half, but dissipates just a few meters beyond the target, The effort leaves Master Liang with a tremor in his hand, hinting at the mental and physical fatigue caused by the technique. As an average Sword Master, his control over 'Qi' is impressive but bounded by his mental stamina and the finite nature of his internal 'Qi' reserves.

Sword Master using Qi Bullets:

In the shaded grove beside the flowing creek, Master Zhang faces a practice array that his disciples have prepared. Before him are thin, tall reeds, each about the height of a man and as thick as a finger, placed at intervals along the bank. They are intended to mimic the silhouette of an opponent, offering a target that demands precision

Master Zhang focuses, drawing the 'Qi' from the depths of his being. It's a familiar sensation, like drawing water from a well. With a series of measured breaths, he raises his hand, fingers outstretched. He channels the 'Qi', concentrating it into projectiles the size of long beans, each about four inches in length and an inch in diameter.

He flicks his wrist, and the 'Qi Bullets' are loosed. They shoot forth with a faint hum, traveling in a straight line toward the reeds. The effort is akin to throwing a dart—a momentary exertion of energy, a subtle tensing of the muscles, and then release. Each bullet finds its mark, leaving a clean hole through the center of a reed. Master Zhang’s breathing remains steady, though his concentration and reserves are noticeably diminished when firing at the more distant reeds.

The reeds sway slightly from the impact, the neat holes evidence of the Sword Master's accuracy. His disciples note that the use of 'Qi' in such a focused manner allows for a quick succession of strikes. The distance and precision can be varied, controlled by the amount of 'Qi' and the sharpness of focus.

Answer 1

Somewhat of a frame challenge:

Have your sword masters have the ability to manipulate the Qi shape, and adapt it impromptu.

Pupils, during traditional training, might be taught specific shapes of Sword Intent, like the Blade and Beam, that tend to come more naturally, and might have a history of recorded movements and meditative techniques that make them more readily available and dependable; shapes that are perhaps somewhat natural extensions of the mental and physical projection they require.
But pupils are soon taught to adapt it to any situation through a training that makes use of changing and increasingly difficult circumstances: targets of increasingly extreme sizes, shapes, and speeds, at locations that are increasingly hard to reach and precarious.

There were a few pupils who stood out, however. Some noticed sooner rather than later, or never, the profound connection between their movements and the energy they were able to project; how they were able to bend and reshape that energy by concentrating on the trajectory of the Qi force, by channeling it towards the dimensions and shape of the target - fashioning it, in short, to their will.

A rapid succession of Qi projectiles will exert the body more, as the already controlled and powerful gestures need to be performed rapidly.
Larger arcs of Sword Intent might require the entire body to be involved.
Larger volumes and a longer duration of Sword Intent might in turn require prolonged concentration, whereas higher speed requires more intensive concentration.

Nevertheless, to answer your question, yes, it does make sense for the Sword Masters in your world to use Qi in a Beam form, even when they have access to Qi blades and Qi bullets: no matter their objectives, (lethally) injuring others is not always the best way to reach them. A beam can knock out a group of enemies. But Sword Intent is not even only useful against enemies, but can also effectively clear paths and destroy obstacles, as your writings show, or help in a myriad of other ways (by extinguishing fires, opening doors and locks, lifting objects?).

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This introduces a new minor obstacle, namely that you have to decide how energy is consumed dynamically (based on volume, speed, rate of repetition, I guess), but you can have a behind-the-scenes formula, cheat sheet, or simply an overview to keep all instances consistent.

Answer 2

You're trying to balance your magic system

And that's a common question type here.

As written, no Qi user in their right mind would use the sword/beam manifestation. Why choose a more limiting solution when a more flexible solution can be had far more frequently?

In my opinion, you have the relative ability to use the two manifestations backwards. Qi Bullets should be harder to produce because they are not connected with the body and what connection they have grows harder to maintain the further the bullet must travel. Because they are disconnected from the body, the level of concentration to create them is higher. Thus, it's easier to create the sword/beam and easier to maintain it. Consider limiting sword manifestations to 8-10 times a day and bullet manifestations to 4-6 times a day. Also consider that it should take longer to bring the bullet manifestation into being, making it less valuable during close-quarters combat.

When balancing your magic system, manifestations of magic should serve specific purposes. In other words, you need to create the purpose before you create the manifestation so you know better how to limit the manifestation. Changing the limits as I've described would lead to a more balanced use of the two manifestations. If they are not balanced, it would more often be due to choices made by the users to bring a favored manifestation to bear (such as adopting stealth to allow for obtaining the "high ground" so that bullets make sense).

Answer 3

Range and Ability to Hit Multiple Targets

It seems there are very good reasons Sword Masters would use the beam form. Here are some cons of the blade and bullet:

Cons of the Blade Form

• Qi is stuck to an object, so it only moves as fast as you move that object
• Low range, for the same reason

Cons of the Bullet Form

• One target per bullet
• Inability to cut things easily

The Qi beam can move quickly with a large range, so it can hit an opponent before the opponent can use a Qi bullet. The Qi beam can hit multiple targets easily, which could be helpful. Finally, the Qi beam can cut things very easily, like the clearing of bamboo in the example given. Perhaps it could even cut stone blocks in two, or small houses for that matter.

The Qi beam is actually very useful.

Answer 4

The Right tool for the Job

A Sword Master can be presumed to be well-versed in all manner of Combat and would think carefully about how they deployed their skills and Weaponary.

So, let's think of some scenarios to demonstrate when/why they might use this.

A Sword master goes to a hostile power as part of an envoy to cease hostilities. The Enemy is a very proud martial nation with a big army and believes in Might is Right - seeking to conquer the smaller dominion where the Sword Master(s) reside.

The Enemy knows a little of the abilities of Qi - but Scoffs that such a small number could stand against their army. So the Sword Master asks with the leaders permission, a demonstration, and asks for 200 prisoners who are condemned to death to be brought forth. The enemy leader scoffs at this and says his Archers/cannons/other could easily kill 200 prisoners. So the Sword Master then places a child (bonus points if it's either the enemies son or the sword masters own pupil) - and then in an instant, cuts all the Prisoners down, but leaves the child unscathed (through manipulation of Qi)

Another example - your Sword master was kidnapped whilst they were asleep and find themselves in the deepest, darkest dungeon of the inner-most keep. They can't use Qi Bullets, They have nothing to wrap a Qi Blade about - but a Qi beam that they could cut an opening and escape out of - now there's an option.

The other thing to note is the thinness of the beam - this means it could be used somewhat like a scalpel - think of it like using a small precision guided bomb instead of using a larger dumb bomb. The Dumb Bomb being a Bullet/Blade, but the beam, with it's narrow blade width could precisely slice things off at a distance (ropes holding a drawbridge up, or the enemy commanders hand as he draws in for Hand-to-hand combat)

To Conclude

Usage of the Beam technique represents a high risk (mental and physical fatigue, using Qi Reserves) and high reward technique and so would be unlikely to be used regularly - but in the right circumstances, it would be invaluable - and that's why it would be used.