Fig.: a person who wields power behind the scenes

The President's best friend is his éminence grise. He has enormous influence over the President, though he is rarely in the public eye

Il miglior amico del Presidente è la sua eminenza grigia. Anche se si vede raramente in pubblico, ha un'enorme ascendente sul Presidente

The title was given to the Capuchin monk François Leclerc du Tremblay (1577-1638), aka père Joseph (Father Joseph), trusted advisor and occult minister of foreign affairs for Richelieu. Given that Richelieu was known as éminence rouge (red eminence) because of the color of his cardinal robe, the Capuchin became éminence grise (grey eminence) after the color of his tunic