consigliere

A consigliere is an advisor or counselor, especially one who serves as a trusted confidant to a powerful figure.

The term comes from Italian and is most associated with organized crime—the consigliere advises the boss on strategy and mediates disputes: He served as consigliere to the don for twenty years.

The word entered mainstream English largely through *The Godfather* and now applies broadly to any behind-the-scenes advisor: She's been his political consigliere since his first campaign.