Krampus is a horned, goat-legged figure of Alpine folk tradition, particularly associated with Austria, Bavaria and neighbouring regions, who accompanies Saint Nicholas on his December 5th and 6th feast, punishing badly behaved children with birch switches, chains and a sack in contrast to the saint's own rewarding of well behaved ones.
The pairing reflects a widespread folk pattern across European Christian calendar custom in which a saint's gentle, rewarding function is balanced by a frightening companion figure who handles correction, a structural role shared by other regional companions of Saint Nicholas such as Zwarte Piet in the Low Countries and Knecht Ruprecht in parts of Germany, though Krampus is distinguished by his more overtly demonic, horned and hoofed appearance drawing visibly on pre-Christian Alpine folk imagery of wild, goat-like nature spirits.
The Krampuslauf, a Krampus run in which costumed participants parade through town streets in elaborate carved wooden masks and animal hides, remains a genuinely observed, actively performed community tradition across the Alpine region today, rather than a historical curiosity, and has spread internationally in recent decades as a distinct winter folk event separate from more commercial Christmas custom.