Crystal Harness

Description and mechanism.

Crystal Harness compose of a chamber containing two pistons opposed to each other and a place for the crystal. The crystal is placed into a designated slot and closed behind reinforced glass to allow visibility on the status of the crystal. The pistons are connected to springs of various strengths. Which are in turn attached to a mechanism operated by buttons and a lock to prevent accidental activation.
When the lock and one of the buttons are pressed at once, the corresponding spring is released, applying pressure on the pistons, which apply the pressure on the crystal.
This way, a requested amount of energy released from the crystal can be manipulated by activating correct springs, or by activating more of them at once. The springs however need to be periodically checked as they get weaker over time and then do not generate as much pressure as they should.
The amount of energy available varies crystal by crystal and depends heavily on the mass of the crystal. The heavier a crystal is, the more Flow is available inside it.
A heavy smaller crystal can have a much greater value than a larger less heavy one.
The chamber is worn at any part of the body, to which it connects by leather straps. Each Crystal Harness is created for specific needs of each Raider. Due to this, they vary in size from the most common ones, which are borne at the wrist, up to massive ones carried on the back of the user.
Larger, more massive versions are used in daily life on Atocites, where the released Flow is directed by specific pipes and then used for refining the resources from raids.

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Usage

When crystals are harnessed this way, the Raider has a steady source of ambient energy to draw for his techniques and abilities. And even though some energy is lost in this way, the user is not distracted by focusing on drawing energy out of the crystal and can instead focus on combat. 
Much more demanded are Crystal Harnesses for Refiners and for the common life. Where the energy from the crystal is used completely and does not require intense and dangerous training of channeling the Flow all by oneself. These Industrial versions of Crystal Harnesses are considerably larger and do not require strictly unmovable and cut crystal in their chamber. Due to this, the industrial Crystal harnesses can be filled with all sorts of crystals, crystal shards, or scraps that remain after the crystal is gently cut to fit the Crystal Harness of Raiders.
For industrial needs, the Flow is also piped and controlled to achieve the desired effects. Though Raiders go through intense training when they develop abilities refiners need only some basic training to shape the Flow by influencing it with their will.

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Discovery

When the Corruption started crystalizing the Flow, people discovered that the crystal are versatile storage of energy, ready to be tapped into.
The issue, however, came from the hard-to-control raw energies released from crystals.
Experiments with crystals were expensive at first, but they were also the number one priority for many. Because of how efficient crystals were in terms of weight-usability. Their only drawback was the hardship of getting them. As they only appeared in places with corruption or as parts of monsters.
The lucky researcher, who threw the crystal at a wall in a moment of rage, discovered that crystals release a small amount of energy when exposed to pressure. It then became a question of how to apply a controlled amount of pressure on the crystals with a device.
With research on crystal being such a priority it did not take long until the first Crystal Harnesses appeared.
It took several years before Raiders started experimenting with crystals, trying to become stronger.
After some succeeded in developing special elemental abilities fueled by crystals, it became important to make the Crystal harnesses small enough to be carried by a person.

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Materials

Crystal harnesses are already complex enough. And their core mechanism is as simplified as it can get. The more complex ones are used for industrial use or places where there is enough time for extracting the Flow from crystals.
Due to the complexity and mechanism required for working of Crystal harness, it is impossible to build one during the raid or even fix a broken one without possessing the required parts, which are usually cast from metal.
The core functionality of the crystal harness is achieved by a combination of the following:
Sturdy chamber to withstand the pressure of pistons, usually build from metal.
Transparent material to see the state of the crystal inside. Easily achievable with glass.
Straps or mechanisms for holding the crystal in place.
Straps for attaching the chamber to the Raiders body.
Robust and hard enough material for pistons. Must be strong enough to withstand the opposing force from sharp crystals.
Material strong enough to provide the force for piston, while being malleable enough for the creation of springs.
Delicate metalwork for the inside part of the spring activation mechanism.

Industrial and household Crystal harnesses are much bigger than their handheld counterpart, which increases the amount of material needed for building one. Apart from that, there might be additional needs:
Metal for any tubing for the released flow.
Coating made from crystals and monster blood to ensure the Flow does not phase through the tubing.