Behind-The-Scenes Influencers

noun a person who exercises power or influence in a certain sphere without holding an official position

• The gray eminence behind the scenes orchestrated the entire political campaign.
• The gray eminence is the one pulling all the strings in the company.
• That gray eminence is the real boss around here.
• The shadowy figure acted as the gray eminence, manipulating events from the sidelines.