Now I do believe their maybe overlap of some of the arcanum powers such as rain could be part of the sky arcanum as storms are part of it but water also falls under the ocean one as well.
They have six /7 arcanum
The 7 is darkness but what it does is use the death of creatures and/or use of items of the other arcanums to power its magic.
Now Sun gives the abilities of light, heat, fire saand so forth.
Moon is illusions, stealth and images. in the way the moon reflects the light of the sun so the moon makes images adn so forth.
Sky of course is air, lighting, storms and so forth.
Those are the ones that have been used in the show so far in any detail.
The one I am not sure of is stars and what would powers be like for it.
So any suggestions as to abilities or spells associated with these powers. I also want to use a term other than arcanum though elements don't seem to quite fit either.
As for races I am thinking so far:
Moon elf - moon arcanum
Sun elf - sun arcanum
Dwarf - earth arcanum