Saint Bernard of Clairvaux (1090 AD-August 20, 1153 AD) helped to reform the Cistercians and greatly enlarged the order, founding over 160 Monasteries. He was an advisor to the Kings of France and fought against the Albigensians Heresy. The Albigensian dualists believed in two gods: one good, who created the spiritual world; and one evil, who created the material world.
He was canonized by Pope Alexander III in 1174 and was declared a Doctor of the Church by Pope Pius VIII in 1830.