Éminence grise

An éminence grise (French pronunciation: [eminɑ̃s ɡʁiz]) or gray eminence is a powerful decision-maker or advisor who operates "behind the scenes", usually in a non-public or unofficial capacity.

The original French phrase referred to François Leclerc du Tremblay, the right-hand man of Cardinal Richelieu, the de facto ruler of France.

An 1873 painting by Jean-Léon Gérôme, L'Éminence grise, depicts him descending the grand staircase of the Palais-Royal–originally called the Palais-Cardinal when it was built for Richelieu in the 1630s–engrossed in reading a book as an array of courtiers bow deeply towards him.

[4] In Henri-Paul Motte's painting of the Siege of La Rochelle (1881), Leclerc is dressed in brown and hold's Richelieu's red cardinal's hat.

Leclerc is referred to in Alexandre Dumas' The Three Musketeers as the character Father Joseph, a powerful associate of Richelieu and one to be feared.