Fair for Its Day: Lothar being an African prince as well as the team muscle may seem very stereotypical. But compared to almost any other black characters in the forties and fifties, he was portrayed with much respect and dignity.
Lothar was originally just a Scary Black Man who accompanied Mandrake like a servant, carried luggage and beat people up if the plot called for it; he also tended to vanish whenever he wasn't needed in a story. Upgrading him to an independent and smart True Companion with lines and his own background story was a pretty huge advancement.
Germans Love David Hasselhoff: Although he will never be quite as beloved in Scandinavia as Lee Falk's other creation, The Phantom, Mandrake is a very popular backup feature in the Scandinavian Phantom comic books.