Paul David Magriel Jr. (pronounced Ma-grill) (July 1, 1946 – March 5, 2018) was an American professional backgammon player, poker player, and author based in Las Vegas, Nevada. Magriel became New York State Junior Chess Champion (January 1967) at the age of 20, while a student at New York University. Backgammon Known as X-22 on the backgammon circuit, Magriel arguably won more major backgammon tournaments than any other player in the world. He was widely considered the world's premier backgammon teacher, an original and clear-thinking theorist and one of its best players. The sobriquet X-22 originates from Magriel's simulation of a real backgammon tournament (compare simultaneous exhibition in chess) with 64 boards, designated X-1 through X-64, in which the player designated "X-22" has eventually won. Magriel first came to prominence on the backgammon circuit when he won the World Backgammon Championship in 1978. From 1977 to 1980, he wrote weekly backgammon columns for The New York Times. Paul and Renée Magriel (his first wife, later Roberts) wrote two books, Backgammon, widely considered to be the bible of the game, and an abridgement for beginning players, An Introduction to Backgammon: A Step-by-Step Guide. Magriel was featured in the commentary in the televised backgammon series, High Stakes Backgammon, produced from the 2005 World Backgammon Championships held in Monte Carlo. It was the pilot series that led to the World Series of Backgammon and showcased Magriel's oratory skills. Poker Magriel had several notable finishes in poker tournaments from the mid-1990s in Europe, playing in London, Paris and Vienna in Omaha, hold'em and seven-card stud events. He won the €2,000 no limit hold'em event at the Aviation Club de France in September 2002, defeating a field including Pascal "Triple P" Perrault, Patrick Bruel and Simon "Aces" Trumper on the way to the €48,600 first prize. In March 2003, he made his first World Poker Tour (WPT) final table, finishing 4th in the $5,000 no limit hold'em World Poker Challenge event in Reno. Magriel finished in the money eight times at the World Series of Poker (WSOP), which includes one cash in the Main Event in 2010, he has also made the final table on the Professional Poker Tour and Ultimate Poker Challenge. Magriel created the "M Principle" (better known since as the M-ratio) - a theory elaborated on at great length in the book Harrington on Hold'em Volume II by former WSOP Champion "Action"