White knight

A corporation that is the target of a hostile takeover sometimes seeks out a white knight that comes to the rescue by making an offer to acquire the target company in a friendly takeover that suits the needs and goals of the target's management and board.

The hostile acquirer is called a black knight, and if the white knight is outbid by a third potential acquirer, who is both less friendly than the white knight and more friendly than the black knight, the third bidder is called a gray knight.