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1.
Made famous by Dan Brown's book "The Da Vinci Code". The orginization was created as a fraud in the late 1960s, though it continues to exist as a myth.
"Did you know Isaac Newton led the Priory of Sion"
"Dude, that ain't real"
by Momoka September 27, 2006
 
2.
The Priory of Sion was/is a brotherhood that keeps/kept an ancient secret concerning the heritage of Jesus Christ and The Holy Grail. They established the Knights Templar and cherged them with excavating the site under Herod's Temple in search of the grail itself.
He was the leader of the Priory of Sion.
by skinanbones08 March 08, 2005