As his name implies, this character is just a voice in Kas' head. In Kas' words, here's a bit about this mysterious Voice.
It sounded like a whisper in my ear, familiar somehow. After a moment, I realized that I recognized it. I had heard it several times before, warning me about things. I’d always listened to it before
There isn't really a whole lot I can say about this character, other then that it's one you need to "keep an eye on", if you know what I mean.
*** small point of clarification: In this story, there are several different "voices" that are used. The Voice, above, is the one that has always warned her about things. The other voices are both masculine and feminine, but I'm not going to give away which is which. Let you guys figure it out!