Light and Shadow

The soul, knowledge, the will, the sense of self, these things are light. Emotion, instinct, and the determination to survive, these things are shadow.
Light comes from the Source of All Light. True Light, Source Light, grows from itself. When life begins, a bit of Light separates from the Source, and a bit of Shadow joins to it. They live their lives together, and when the creature dies, the Shadow escorts the Light back to the Source it came from. Shadows repeat this journey many times, but a Light only makes the trip once.
That's how it went before science started to interfere, of course.
Etherion is a lesser form of Light. It cannot autonomously grow more of itself, but people discovered you can make more of it by bonding it with a captured, Lightless Shadow. Arketts use special crystals to capture both Etherion and Shadows. The crystal can hold a bit of Etherion, which attracts a Shadow. Once the Shadow is bonded, the crystal can hold far more Etherion, and that energy can be used to power all sorts of technology, just like a rechargeable battery.
The Arketts use that same kind of bonded, captured Shadow to produce more Etherion. They place it in a specialized chamber and introduce more Etherion than the Shadow can hold. The Shadow cannot grow to contain the additional light, and the two are forced apart. The separation releases unrefined Etherion, which is siphoned out of the chamber. Then the Shadow and the Etherion are allowed to crash back together, which produces even more Etherion, which the Shadow cannot hold, and the cycle repeats.
The Order of Cadmus will steal that technique and use it on Source Light, an actual living being. They initiate the first separation through extreme torture, and the cycle perpetuates itself far longer than it would with Etherion. Eventually, in either case, the Shadow gets worn out and becomes a Husk, or a darkness that refuses to bond any kind of light.

Manifestation

There are not different kinds of shadows but there are different kinds of light. True light is warm, self sustaining, and all around us. Artificial light is cold, quick to dissipate, but can be melded into things of everyday life, stored in certain kinds of things or people. Artificial light is an imitation of what nature and evolution has given us. It may help us in the moment, but in the long run it can very well lead to our downfall.

Type

Metaphysical, Elemental