The old advisor is the éminence grise behind the company's success.
éminence grise
idiomA secret or unofficial decision-maker.
Origin
Borrowed from French éminence grise (literally “grey eminence”), originally applied to François Leclerc du Tremblay (1577–1638), also known as Père Joseph, a French Capuchin friar who was the confidant and agent of Cardinal Richelieu (1585–1642), the chief minister of France under Louis XIII (1601–1643). The term refers to du Tremblay’s influence over the Cardinal (who bore the honorific of Eminence), and the colour of his habit (grey, rather than the red of a cardinal).
Everyone thinks the CEO runs the firm, but his assistant is the real éminence grise.
Though she held no official title, the veteran diplomat had become an éminence grise whose quiet counsel shaped foreign policy for three decades.
Last updated April 17, 2026