From Warren Robinett's first easter egg in Adventure to the retrogaming scavenger hunts of Ready Player One, mysteries exert a magnetic pull on players. The Binding of Isaac and The Legend of Grimrock bristle with puzzles, traps, and secrets, mirroring the effective but obscure narrative design of the cult classics Demon's Souls and Killer7. Howard, an expert on quests, demonstrates designing mystery through intertwined mechanics and narrative, individually cryptic but mutually reinforcing. Mystery enables puzzles that are pervasive and organic rather than localized and artificial. The cumulative effects heighten player engagement, enrich player communities, and keep satisfied players wanting more.