The freshness of spring is already in the air by February in the Croatian hilltop village of Viskovo. A riotous noise approaches: a cavalcade of bell-ringing, music, and screaming. In a magical-seeming ritual, an army of men in grotesque animal masks dance, draped in sheepskins, armed with axes and clubs. They huddle into a concentric circle and shake their rumps, clattering hundreds of cowbells in unison. They’re orchestrated by a flamboyant commander (the komandante) in an all-white uniform and golden epaulets. A devil clad in black dances on a rooftop,…