What's the technological level? Modern, near future, or space-faring full-on science-fiction? A steampunk or cyberpunk variant? Are there spaceships, orbital weapons, guns, crossbows.... what?

Is the magic divided into particular schools, does it have particular limits, or can we just make up whatever we want?

You stated that the people adapted, and even evolved on both sides of the planet. Wouldn't that mean that there are two 'races'? Snow-people and sun-people?

Also, I like Three. Just, the fact that the cities are One and Three amuses me. I don't know why. It just does.