Some random observations before I forget them (I'll keep it brief), and then a picture.
1. I like the concept of Yin/ Yang
2. It's important to understand the fundamental connection between two seemingly opposite things (like Light/Shadow or Good/Evil)
3. Norse Mythology, while containing many aspects of good/ evil, seems defined by an overarching cyclical order-->chaos--> order, with the idea that the Norse gods represent civilization, the Giants represent the untamed forces of nature (chaos), and that in the end, these giants will fight the gods, and win.
4. It's also important to understand the words you're using. I think I need to shy away from "myth." That has too many connotations of falsities/ untruths/ urban myths.... 'Mythopoeia' is a better word. Yes, mythologies are 'false' (the sun is not pulled in a boat across the sky). But perhaps storytelling, like art (and storytelling is really just a subset of art, of course) is meant to "use lies to tell truths." Picasso said something like that once....
Speaking of sun myths, I have this idea floating around in my head of a world built around Light and Shadow that is slowly being overcome by the "Shadow" side of things. This means the major lights of the world are going to be overthrown. Since I'm doing everything allegorically here, the Sun of my mythopoeia doesn't have to be a heavenly celestial body, but can be, say, a man riding a chariot across the sky with a burning torch.
Low and behold, I do some research and find an awesome painting by Sebastiano about Phaeton, the son of the Sun god Helios who cannot control the chariot and is struck down by Zeus. Perfect composition and subject matter upon which I am basing my own Chariot crash.
And then my own drawing, getting at more of an ambush on the chariot rather than a reckless crash:
(It was awesome to draw large, with vine charcoal, and just focus on composition/ form/ space/ light/shadow/ etc....)