Foil

A foil in literature is a character who contrasts with the main character to highlight the main character’s attributes. The purpose of the foil is to give the protagonist more color, depth, and nuance. So, the kind protagonist has a cruel foil. It's common in novels, movies and comic book superheroes.

A foil is not necessarily an enemy or antagonist. Sherlock Holmes had Dr. Watson. harry Potter has Draco.

But why? We know that a common use of foil is the metal that we use to wrap foods. Jewelers also place foil under gems to make them shine more brightly. Is it because this contrast makes a jewel’s brilliance and facets more apparent. Is that why a literary foil character serves as a "backdrop" to make the protagonist “shine.”

As a noun, "foil" means "very thin sheet of metal". It comes from the Old French words fueille, foile, or fueill, which mean "leaf; foliage; sheet of paper; sheet of metal". These words come from the Latin word folium, which is the plural of folia and means "leaf". The word "foil" has been used since the early 14th century.

As a verb, "foil" means to overthrow, defeat, beat off, repulse, or discomfit. In wrestling, it can also mean to throw or inflict a "foil" upon.