S6, E21: When Archie (KJ Apa) and Veronica’s (Camila Mendes) attempt to negotiate with Percival (guest star Chris O’Shea) doesn’t go as planned, the forces of good and evil finally face off, leading to some unexpected revelations. Lili Reinhart, Cole Sprouse, Madelaine Petsch, Mädchen Amick, Casey Cott, Vanessa Morgan, Charles Melton, Erinn Westbrook and Drew Ray Tanner also star.