Who is Bark (Mohammad ben Lhaoussin) from Wind, Sand and Stars and what is their importance?

The Marrakech-native slave the men called Bark at one of the forts in the Sahara is a source of moral compulsion for Antoine. He finds himself compelled by his determination among submitted slaves to retain his own identity and the hope of his eventual return home. Bark asks at the beginning of every evening whether he may be smuggled on the next plane to Marrakech and then continues to serve faithfully without another word.