Rukh (Rue-Kh)

Rukh is the home of souls. While we live, it is every man for themself. But when you die, all go back to one place, This is Rukh. When humans die, their bodies return to the earth don't they? The souls return to Rukh, The home of souls.

— Armoni Ziran, Priest of Vras

Rukh is a mysterious thing. It is neither a being nor a phenomenon, yet it is what makes both. The rukh is thought to be the souls of beings that died, the final resting place of one's soul.
The rukh is what allows mages and sorcerers to interact with the weave of magic. The rukh generates energy called magoi, which can be concentrated and fired to create different phenomena. All living beings have Magoi inside their bodies, but only certain people with certain objects can call forth this power. A spellcaster can communicate their intent and the effect that they seek to create, and the rukh will translate that intent through the weave into a magical phenomenon.
The rukh is seen as the greatest and final creation of the former deity Ethio.

Manifestation

Rukh appears as small butterflies or birds made entirely of light. These "beings" can interact with the world around them, however, the world cannot interact with them directly.
Not only this, but the rukh is not always visible for every being. Only when concentrating can one see the true essence of the rukh.