Do you want Zexion to be able to pick up on your character's Light/Darkness balance?
Sure


If so, what is it like? Are they generally more positive, or negative?
It is a dark fox spirit hiding out in a magically made human body. Given that it is an agent of Chaos and feeds on pain/hate/strife, it's probably pretty dark. As for Light and Darkness of the heart, it probably doesn't have any since it is an animal and is stated in canon to not understand right/wrong good/evil or even give a damn about those things. It understands how to hurt humans and feed off them, how to smash Order. I don't know if that helps?


Optionally, what do they actually smell like? Eastern incense with fox.

Additionally: It is a possession, kinda sorta? It made the body as a copy of Stiles, but it is a spirit in control of a body in the end.