Knight Templars Seal. The order of the Knights Templar is synonymous with the crusades of the Middle Ages. This section of the Middle Ages details the emergence of the Religious knights, their achievements, accomplishments and their decline on Friday the 13th, in October 1307 when Jacques de Molay, the Grand Master of the Knights Templar, and 60 of his senior knights were arrested in Paris. It is the reason Friday 13th is deemed to be unlucky. http://www.middle-ages.org.uk/knights-templar.htm