Set is the biggest and the baddest of the gods—or so he likes to think. Compared to Apophis, though, he's small stuff. In fact, according to Nut, Set was never truly evil: "In the old days, he was Ra's strongest lieutenant. He protected the sun god's boat from the serpent Apophis. Now there was evil" (20.47). You can't be evil if you're fighting against evil, right?
In fact, Nut presents a pretty nuanced picture of Set—though of course she's biased, because she's his mom, after all: "He has done horrible things, yes. It is his nature. But he is still my son, and still one of the gods. He acts his part" (20.64).
Whether you call him the Red Lord, or the evil bunny god as Sadie does (7.223), Set is powerful and frightening. Before Sadie and Carter truly get a sense for who Set is, Carter recalls from his mythology knowledge: "Set was a really bad dude. Like, the villain of Egyptian mythology. The god of evil and chaos and desert storms" (7.216). Sounds like he has a winning personality.
Set is also quite tricky: Sadie sees in a vision how he presented Osiris with a beautifully crafted box, saying that only the person who fits inside deserves to be its owner. This is apparently too awesome a box to resist, since Osiris fell for it, and Set imprisoned his brother indefinitely.
When Set first manifests in the mortal world, he looks like a dude on fire. He also looks like he can't quite make up his mind what he is or which world he's in. Carter describes him like this: "It was as if someone had superimposed two different faces on top of each other—one almost human, with pale skin, cruel, angular features, and glowing red eyes, the other like an animal with dark fur and sharp fangs" (2.99). Yep, pretty freaky-looking.
One thing Set and Horus have in common is their rage: both of them will light up with anger in an instant. And they love a good fight. Set is smiling and laughing the whole time he's battling Carter/Horus on top of the red pyramid. We're betting he hasn't been in a fight this good since before he was imprisoned in the Rosetta Stone.
Of course, Set is also really arrogant, so he refuses to believe that he was being used by Apophis the whole time. He accuses Isis of being up to her usual tricks before finally accepting that he needs to ally with the other gods to beat Apophis in the long run.
Would you trust Set on your side? Carter and Sadie aren't that stupid, but they don't really have a choice. Anyway, they have his secret name (Evil Day), so in theory, they can bind him to their will. We're keeping our fingers crossed, because Set sure isn't make going make it easy for them.