Winter has finally come! Discover the frozen mysteries and chilling dangers of the nation of Irrisen, the Pathfinder campaign setting's realm of hearty heroes, merciless magic, and icy evil. Confront the freezing ambitions of the land's proud rulers, the winter witches; hunt magical monstrosities born amid endless blizzards; and learn the cycle of the realm's frigid rulers, the infamous daughters of Baba Yaga. With details on the nation's major settlements, sinister adventure sites, new rules for wintry dangers, hosts of icy monsters and native NPCs, and plots to inspire whole campaigns, this shiver-inducing sourcebook gives GMs everything they need to adventure across this realm of wintry wonder. All the details on Irrisen's dangers and denizens also makes this the perfect companion for GMs running the chilling new Reign of Winter Adventure Path. Unleash a storm of icy evil upon your campaign with Pathfinder Campaign Setting: Irrisen -- Land of Eternal Winter!