Paraskevidekatriaphobia

Rico says everyone's afraid of Friday the 13th (they've even made a dozen movies about it), but for all the wrong reasons:

On Friday, 13 October 1307, hundreds of the Knights Templar were arrested in France, an action apparently motivated financially and undertaken by the efficient royal bureaucracy to increase the prestige of the crown. Philip IV was the force behind this ruthless move, but it has also tarnished the historical reputation of Clement V. From the very day of Clement V's coronation, the King falsely charged the Templars with heresy, immorality, and abuses, and the scruples of the Pope were compromised by a growing sense that the burgeoning French State might not wait for the Church, but would proceed independently.