black knight

1. Someone, usually a villain, who intentionally hides their identity, as by eschewing heraldic symbols. A black knight is usually nefarious. Why else would he try so hard to hide his true identity? That shifty-looking guy always struck me as a black knight, even before he betrayed the main character. If they have no recognizable insignia on them, they might be black knights. Steer clear.

2. In finance, a company that is trying to acquire another company without the approval of the latter's board of directors (a process also known as a "hostile takeover"). It turned out that a black knight had been orchestrating a hostile takeover when the CEO's back was turned. That wealthy foreign company is indeed a black knight looking to grab at a majority shareholder position of the media conglomerate in order to take control of the board. Reading between the lines, it looks like the black knight is poised to take the company over.