Who is Mr. Thomas Russell from Two Years Before the Mast and what is their importance?

Mr. Thomas Russell is a short, round-shouldered, red-haired, one-eyed, vulgar-looking man, who is added as an officer aboard the brig Pilgrim just before her voyage to San Pedro, CA. The common sailors dislike Russell, even before he assists Capt. Thompson in flogging Sam and John the Swede. Russell eats and sleeps alone, and does little else. He is later dismissed for misconduct.