How Do You Make Your Side Characters So Interesting?

One of the aspects of writing characters like them is that if we’re not going to get viewpoints from them, their personality has to be strong enough to manifest externally. Which tends to have an effect, if it’s not done well–or sometimes even if it is done well–of making them feel one-sided. In some ways I play this up; for instance Nightblood really is one-sided because of the way his personality works, the way he was crafted. He’s a construct, and he has a main focus.