Who was Elias Hoseaseon in Kidnapped?

Kidnapped, an 1886 novel by Robert Louis Stevenson, tells the story of a teenaged orphan and his adventure to gain his inheritance, help and be helped by Jacobite rebels, and stay alive. A notable opponent of all these goals is one of the book's antagonists, Captain Elias Hoseaseon of a ship named the Covenant.
As the name of his ship suggests, the Captain is said to be a religious man, though he is incredibly selfish and greedy. He is sold our protagonist, David, by David's uncle, who has asked Hoseaseon to sell David into slavery so that he can't claim his inheritance. Hoseaseon complies with this without much thought or moral difficulty.
Despite Hoseaseon's cruel intentions for David, David still manages to see his humanity in the way that Hoseaseon truly loves to sail and loves his ship, the Covenant. While this reveals David's ability to empathize with others, and Hoseaseon's more complicated nature, it hardly compensates for his actions, which include not only trying to sell David into slavery, but also his passiveness in the murder of Ransome and Hoseaseon's conspiring to murder Alan.