Henry the traitor
Henry is a former slave who betrays his community by attaining his freedom and then instantly turning around and buying slaves for himself. Instead of realizing the evil of the institution, he realizes what is tempting about it, that it is a power trip, that it leads to wealth through exploitation. These are enough to entice him into forsaking his fellow man and turning against them, owning slaves as a former slave himself.
Caladonia as a symbol
Caladonia is a woman who has a chance to restore the balance after Henry dies, leaving the estate to her, his wife. She and Moses have a amicable relationship, but in the end she reveals that she has the exact same intentions as her husband did, showing that Henry's symbolic self-betrayal is a problem that has either infected her, or perhaps it was always there as it was in Henry. Together, they symbolize the commonness of such betrayal.
Moses as a symbol
Moses believes with blind hope that perhaps he will get to be with Caladonia as a free man. He is somewhat abusive himself, and he is no more of a good person than Henry. He is the overseer of the slaves and something of a suck-up, and he believes that he might earn freedom through this, but he doesn't notice that they don't view him as a human. He is a symbol for the desire for power.
Slavery and freedom as motif
The dilemma of freedom hangs over the slaves as a kind of tease. Some are freed and educated, but they simply adopt the hateful attitudes of their previous owners. This motif paints a picture of freedom is seen as a privilege instead of a right, underscoring the injustice of the whole endeavor. The fact that some people attain freedom without understanding that they were entitled to it by nature is another indication of this.
The mixed race children
The half-black, half-white children are a living symbol that the systems of racial injustice are foundation-less and evil, because they are predicated on ideas about race that are obviously false. If the children of black and white mixed race couples are healthy viable kids, that is nature's sign that black people and white people are literally the same animal. The color of a person's skin is absolutely irrelevant to nature, but it had become relevant in America because of institutionalized racism.
