Professor James Moriarty is Sherlock Holmes' arch enemy (chief enemy). Moriarty commits many crimes. He is a mathematical genius and worked at a small English university, before he quit and moved to London. There he became the center of organized crime (the mob) and the object of Sherlock Holmes's investigative power who considered the professor his intellectual equal. Sherlock Holmes vs (against) Moriarty represents one of the greatest battles of wits (shrewdness, intelligence, smartness) in the history of the world. Holmes spoke often of Moriarty's genius in admiration in spite of (not considering) the horror of the crimes. He spoke well of Moriarty without taking into consideration the evil side of his nature. Among Holmes other foes is Moriarty's Chief assassin Colonel Sebastian Moran ["The Adventure of the Empty House']; Dr Grimesby Roylott; ["The Adventure of the Speckled Band<nowiki>"</nowiki>]; Roger Baskerville aka Jack Stapleton ["The Hound of the Baskervilles"]; Charles Augustus Milverton ["The Adventure of Charles Augustus Milverton"]; John Clay ["The Adventure of the Red headed League<nowiki>"</nowiki>] and Irene Adler ["A Scandal in Bohemia"]