One of my big challenges in the geography of this world was figuring out how we could have a kingdom set at the pole of the world while at the same time maintaining a normal day/night cycle. My original plan was for the Well of Ascension to be located a distance to the north of Luthadel, up at the geographic north pole of the planet. When I was revising the second book, I realized that wouldn’t work for various reasons. (More on this on the MISTBORN 2 Alternate Ending deleted scene page.) I changed things so that when the Lord Ruler held the power in the Well, he decoupled the geographic north pole and the magnetic north pole.
In our world, the magnetic north pole is located about eleven degrees of latitude south of the geographic north pole. On Scadrial, the two poles were originally in the same location. When the Lord Ruler moved the planet too close to its sun and realized he didn’t have the control to place the planet in the proper orbit, he created the ashmounts to cool the atmosphere. He also wanted to keep access to the Well under his control, so he decided to build his capital city right above it. However, he realized that on a planet with a tilted axis, a city at the north pole would have seasonal daylight variation so extreme that at the height of summer the sun would never set and during the dead of winter the sun would never rise. He could remove the axis’s tilt, but that would just make the sun perpetually skirt the horizon all year round.
What Rashek decided to do (and he had to make split-second decisions in the brief time he held the power) was to shift the crust of the whole planet so that the Well was at a latitude that would have more standard seasonal variation, and to re-create the Terris mountains in the new North (to maintain the rumors that the Well was located there). He worried that the new location of Luthadel would be too hot due to the latitude, but it turned out that moving the Well created an unexpected effect. The planet’s magnetic pole followed the Well as he relocated it—and the ash from the ashmounts was slightly ferromagnetic. (Ferromagnetic volcanic ash has some precedent in our world.) So the interaction of the ash with the planet’s magnetic field’s new alignment meant that its protective cloak over the area of the Final Empire caused it to be cooler than the now unprotected geographic north pole.
One side effect of this is that all compasses point toward Luthadel. Since it’s been that way for a thousand years, no one finds it odd–in fact, it’s used as evidence of the Lord Ruler’s divinity. It also makes it mathematically very easy to pinpoint one’s exact location in the Final Empire using a combination of the compass reading and noon observations. Not that it’s easy to get lost in the Final Empire in the first place—the geographical area of the planet’s surface that the Final Empire covers is actually quite small.
Ultimately, when it comes down to sophisticated geography and astrophysics, I’m out of my element. If there are mistakes in my reasoning above, that is why I write fantasy and not hard sf.
And I still haven’t said anything about what happened at the south pole.
“Something in the form of that which we’d seen before.”
There’s one other cool item to note in this chapter. If you read Ruin’s words carefully, he admits that he has indeed seen human life somewhere before. This means that there is life on other planets in this cosmology, and that Ruin and (presumably) Preservation have experience with those other planets.