What is the origin of the idiom "beard the lion in his den" and when to use it?

The phrase "beard the lion in his den" originated from Shakespeare's play "Richard III" and refers to the act of confronting a powerful opponent or authority figure in their own territory or domain. It symbolizes the courage to face a formidable challenge or danger head-on. It is commonly employed in situations involving challenging authority figures, taking on formidable opponents, or standing up to influential individuals in their own stronghold.