Carter Kane's whole life is in his suitcase. Traveling with his Egyptologist dad, he's never really had a normal life: all his possessions fit in a suitcase, he's homeschooled by his dad, and the two of them never stay in once place for long.
Carter's relationship with his dad is also pretty special. For one thing, he's learned to trust and obey his father. When Carter admits to Sadie that he's never peeked inside their dad's workbag, Sadie declares: "God, that is so like you, Carter. You're hopeless" (2.54). We're not saying Carter's a total tool, but, well, a bunch of stuff has to happen to him before he'll start to question authority.
For instance, when he learns about Bast being imprisoned at Ra's order, Carter insults Ra, and thus questions the very source of order. This, apparently, is a bad thing to do, since it increases his risk of falling under the influence of chaos. But because something bad happened to someone Carter cares about, he's willing to take some action, even if it's dangerous.
Unlike most kids his age (fourteen), Carter has never had a locker at a school. He's never been on a date. We're pretty sure he doesn't even have a Facebook account. What he does have, though, is a ton of knowledge about all things ancient Egypt. After he goes into information-mode about the location of the missing Luxor obelisk (16.102-104), Sadie nicknames him Mr. Wikipedia—which isn't the most flattering thing you could call a teenager, but it does describe Carter's near-encyclopedic knowledge of Egypt pretty well.
Carter knows that he doesn't fit in with other kids his age: "In fact I've been to more museums than I like to admit—it makes me sound like a total geek" (2.1). News flash: he is a total geek. Here's how Sadie describes him: "[H]e dressed like a junior professor, with his khaki trousers and a button-down shirt and loafers. He's not bad looking, I suppose. He's reasonably tall and fit and his hair isn't hopeless. He's got Dad's eyes" (4.3). It's not that Carter really enjoys dressing this way, but it never occurred to him to do otherwise. Who is there to impress on archaeological digs, after all?
The other reason Carter's wardrobe is old-person chic is that, according to his dad: "You're an African-American man. People will judge you more harshly, and so you must always look impeccable" (6.49). It sucks that the color of Carter's skin influences how he's perceived, but there you go. Racism 101.
Despite being separated for the last six years, Carter is super aware that Sadie's his younger sister—and that he should look out for her. On the night they lose their father, Carter notices "the fear in Sadie's voice. It triggered an unfamiliar feeling in me, like I needed to reassure her. The idea seemed ridiculous. Sadie had always seemed so much braver than me" (5.102). It's probably not easy to feel like a protective older brother when your sister is already such a rebel, but Carter manages.
For instance, the second time Sadie has to turn into a bird, she's freaked out about not being able to turn back into a human. Carter reassures her by taking her hand: "I'll stay with you. I'll make sure you turn back" (21.20). And he does—though we can imagine that not having to hear Sadie's constant sharp commentary might be a nice break.
They end up working together pretty well as a team, which is good since, as hosts of Horus and Isis, they risk being at each other's throats. Because let's face it, you've got to love your family, but you don't always have to like them.
When Zia tests the Kanes' magic, Carter figures out a cool new trick: "He rose off the ground, surrounded by a golden holographic shell like the one Bast had used, except that his giant image was a warrior with the head of a falcon" (16.162). Pretty neat, right?
Maybe Carter never thought of himself as brave before this whole adventure happened, but his heroic instincts kick in when the Set animal attacks: "People were in trouble because of us. I had to fix it. I felt the same kind of instinct I felt when Sadie needed my help, like it was time for me to step up. And yes, it terrified me. But it also felt right" (21.14).
Coming into his own as a warrior is a pretty big deal for Carter. As he battles Set atop the red pyramid, he thinks: "It was a fight to the death, and I felt great. Every move was perfect. Every strike was so much fun I wanted to laugh out loud" (38.1-2). As someone who started as a homeschooled geek, it sounds like Carter's really getting the hang of hosting a warrior god, huh?
That's what makes it so much harder for Carter to give up the amulet of Horus at the end of the book. He does it in order to prove that he's not letting the god take over and use him like a piece of spiritual toilet paper. By doing so, Carter proves that being strong doesn't just mean being able to swing a sword or face down enemies: it means knowing and controlling your own desires and reactions.