A slave for thirty years, Breadbox is the oldest slave in the camp by far.  Old slaves don't sell well, and at this point, they can't even give Breadbox away. Mostly, the Slavers just ignore him.
Breadbox is a slave locked up in the Paradise Falls slave pen, and can be found there the entire day. Should you be able to open the gate and free the other slaves, Breadbox is the only one that will not flee, making him the only slave that can only be found at the pens unless killed.
In a conversation with another slave, he reveals that his nickname comes from a game that slavers used to play with new slaves ("See what'll fit inside a breadbox.") that he'd "rather not talk about" indicating that he or another slave he knew was sexually abused.
He is opposed to the plan to break out of Paradise Falls that Bleak is concocting and urges her to accept her life as a slave and cooperate with the slavers.
Breadbox appears to be incredibly hard of hearing when conversing with the Lone Wanderer but never with the other slaves. This is either an inconsistency or he pretends to be hard of hearing as the negation of the Lone Wanderer's attempts to free him.
He will confuse the Lone Wanderer for a member of the opposite gender, and make advances if the Lone Wanderer is male.