As I previously warned, these posts will contain spoilers, and will give away plot points. Please do not read without being aware of this. This process is intended to enable me to better understand Mistborn as I re-read it, so I'm not going to shy away from spoilers.
In light of that, I am going to put all of the details in these posts after a page break. Sorry for the inconvenience, but I don't want anyone to stumble onto spoilers by accident!
Moving into Part 2, we start with a fun little set piece describing a training battle between Vin and Kelsier that showcases how allomancy works and clarifies some of Vin's potential weaknesses - specifically, that she is smaller and lighter, which impacts her ability to push and pull. Overall, though, it encourages the reader to invest in Vin as a character who is willing to place herself at risk.
Also in this part, Sanderson begins to develop Sazed as a Keeper. We aren't specifically told what a Keeper is, just that Sazed, a Terrisman, is one, and specifically, that he is a Keeper for religion. He is encouraging Vin to choose a religion, by describing them to her:
"The Terrisman nodded his head slightly with respect. “I was wondering if you might be willing to listen to another proposal.”
Vin sighed, rolling her eyes. “Fine.” It isn’t like I can do anything else but sit here.
“I think I have the perfect religion for you,” Sazed said, his normally stoic face revealing a glimmer of eagerness. “It is called ‘Trelagism,’ after the god Trell. Trell was worshipped by a group known as the Nelazan, a people who lived far to the north. In their land, the day and night cycle was very odd. During some months of the year, it was dark for most of the day. During the summer, however, it only grew dark for a few hours at a time."
I don't want to spend a lot of time speculating about Brandon Sanderson's personal religious background, so I'm going to refrain from imputing Sazed's interest in religion to the author. From my perspective as an agnostic atheist (i.e., I am not personally convinced that there is a god, but acknowledge that it is certainly possible albeit not proven that one exists), I find Sazed's approach to religion both interesting and worth discussion. Sazed is a preserver of knowledge, who has taken on the burden of ensuring that religions are not entirely lost, though they may no longer be practiced. When Vin asks him what the point of remembering 562 separate belief systems, he responds:
"Sazed frowned. “The answer should be obvious, I think. People are valuable, Mistress Vin, and so—therefore—are their beliefs. Since the Ascension a thousand years ago, so many beliefs have disappeared. The Steel Ministry forbids the worship of anyone but the Lord Ruler, and the Inquisitors have quite diligently destroyed hundreds of religions. If someone doesn’t remember them, then they will simply disappear."
And he goes on to say that once the Lord Ruler's reign ends, as it inevitably will end, men will want to return to the beliefs of their fathers, and on that day, they will turn to the Keepers.
"Vin asked as Cosahn moved around to begin snipping at her bangs. “There are more like you?”“Not many,” Sazed said. “But some. Enough to pass the truths on to the next generation.”
I always admire it when an author includes religion in their fantasy worlds. As long as there have been human beings, human beings have been trying to order their world, and one of the ways that people do this is by establishing religions. For me, this adds to the richness of the world. And Sanderson has also not shied away from showing how religion can be used to manipulate people - the Lord Ruler claims divine right of rule by virtue of the fact that he defeated a terrible enemy, but Vin, as a result of her conversations with Sazed begins to suspect that it's all a scam.
The section ends with Vin gravely injured after Kelsier recklessly enters the palace with her to look for the stockpile of atium:
“Was this insane stunt really worth nearly getting yourself—and the child—killed?”
“I don’t know,” Kelsier said honestly. He turned to Dockson, meeting his friend’s eyes. “Ask me once we know whether or not Vin will live."
Spoiler alert: Vin lives.