The purpose of creating a Purple Halloween Discount Sale Poster is to advertise a sale event during the Halloween season, with the intention of attracting potential customers and increasing sales. The poster should include eye-catching designs, clear information about the sale, and a sense of urgency to encourage people to act quickly. The use of purple on the poster is intended to create a spooky and festive atmosphere that aligns with the Halloween theme. Overall, the poster serves as a promotional tool to generate interest and excitement about the sale among prospective buyers.