The term “Foil Character” refers to a secondary character within your story who is meant to serve as a contrarian to your main character in some way. This could be through their belief systems, their problem-solving techniques, or even their entire personalities. In the realm of storytelling, the Foil Character is there to help drive the plot or character development and shine a light on what is most important, or what is most difficult, to your main character.
Write a scene involving your main character and their foil. Be sure to address a moment of conflict or tension, however extreme or subtle, that demonstrates their differences and hints at more difficulties to come.