High Side Slit Dresses & Windsor Sexy Black Lace Mermaid Prom Dress Strapless High Side Slit Formal Illusion Evening Dress Floor Length Party Gown High Side Slit Dresses & Windsor Slit Dresses & Windsor. Look stunning in our Sexy Black Lace Mermaid Prom Dress! This strapless gown features intricate lace details and a high side slit for a touch of sexiness. The illusion neckline adds a formal touch to this floor length dress, perfect for any evening event. Stand out from the crowd in this classy party gown. Please note: Accessories such as a veil, sleeves, or crown are not included with the dress.