The Cantici are a tribe that are mentioned twice in the book.
The Cantici are first announced when Varica narrates a story to three slaves. Salvius goes to visit a mine in which the Canticans work. They work hard and extract a lot of iron, but even then Salvius is not satisfied. When he calls all the slaves to inspection, he discovers that one is sick. He further declares "servus aeger est inutilis. ego servos inutiles retinere nolo". After this, he heartlessly murders the slave, even thought he isn't even his slave.