Both. Our souls are made of aether, it is the lifeblood of our star, but we can also harness it to cast spells.

There are six types, one for each of the elements, and should it tip too far in one direction everything can be thrown out of the balance. Not just for people, but worlds as well. For example, one world tipped too far into darkness and is now a void where terrible demons we call Voidsent thrive.