Anthony Cross Saint is a religious figure in the Eastern Orthodox Church. He was born in Constantinople in the late 10th century and was a monk at the Monastery of St. Anthony in Jerusalem. He is known for his writings on the spiritual life, which were influential in the development of Eastern Orthodox theology. His feast day is celebrated on August 15th. The term TAU refers to the Greek letter 'T' which is the symbol of the cross and is often used to represent the crucifixion of Jesus.