He is the Arab or black boy who becomes Robinson Crusoe’s slave. Xury is briefly introduced in a book during the time when Crusoe is liberated from slavery in Sallee. When Robinson leaves the place, he takes another two slaves with him. He makes one of them swim to the shore, but leaves Xury onboard. This detail shows that Crusoe trusts the boy and doesn’t see a possible danger in him.
After all, when Robinson is rescued by the Portuguese captain, he sells his slave. Somebody claims that this is a clear manifestation of racism and double standards, present in Crusoe’s character.