The super-powered alien who becomes the servant of Jimmy Olsen in the 13th century.
Kurol, "of the tribe of the Djinn" comes from "a far world ... threatened with destruction." Before his planet blows up, Kurol and a select few of his fellow tribesmen are rescued by an alien scientist who transforms them into "living vapor" and transports them in bottles to Earth, on the condition that, when released, they will serve whoever opens their bottle.
When Jimmy Olsen assumes the identity of Marco Polo, he finds and opens the bottle containing Kurol. Once released, the alien is revealed to possess powers similar to Superman as a result of his "weird, ultra-heavy molecular make-up." True to his oath, Kurol uses his power to help Olsen/Polo in his quest to reach the court of Kublai Khan, until ultimately returning Olsen to the present in a seeming act of betrayal (SPJO No. 157/1, Mar 1973: "The Strange Second Life of Jimmy Olsen!").
(See also Abdul)