Character Clues
Character Analysis
Names
Custance's name means "constant." Yeah, once you realize that, you feel like a bit of a dunce for not having realized it before. And that word constant symbolizes her most important trait: no matter what happens to her, she remains faithful to God and her Christian faith. She waits patiently upon whatever God has in store for her, never shifting her focus from her ultimate goal, salvation. This behavior epitomizes constancy, or always being steadfast and true. Given all this, it seems pretty clear where Custance gets her name (and what we're supposed to take away from that name).
Direct Characterization
In "The Man of Law's Tale," we learn important information about Custance by hearing what a bunch other characters say about her. The Syrian merchants who visit Rome hear the "common voice of every man" describing Custance as the most beautiful and virtuous woman ever born. Although we can't necessarily always trust rumors we hear in the streets, our narrator assures us that "al this voys was sooth, as God is trewe!" (169).
Other than describing Custance's character, the narrator reserves the bulk of his direct characterization for the bad girls in the tale. One example of this is when he calls the Sultan's mother the root of all evil. Of course, it's debatable whether or not just calling someone "evil" counts as characterization. You could argue that all it's doing is placing them in a moral category, without telling us anything specific about their personality. But since the narrator also likens the Sultan's mother to the serpent who tempted Eve, we can guess that she is manipulative and scheming, which her actions later confirm.
Actions
Most of what we learn about characters in the "Man of Law's Tale" comes from their actions. Custance stays faithful to God despite adversity and prays all the time—she is a pious Christian. The Sultan of Babylon becomes obsessed with a woman he's never met and converts to Christianity so he can marry her against the wishes of his advisers, therefore we can guess that he's impulsive, headstrong, and stubborn.
The "bad" women in the tale—the Sultan's mother and Donegild—lie and cheat in order to achieve their ends, so we can see that they're manipulative and secretive. King Alla correctly discerns a treacherous knight's ulterior motives in accusing Custance of murder; he's got good judgment and is deeply thoughtful. We could go on and on for days, but we bet you're more than capable of coming up with your own examples.