St. Gertrude the Great was a Benedictine nun and mystic who lived in the 13th century. According to tradition, our Lord promised her that 1000 souls would be released from purgatory each time it is said devoutly. Because of the desire to unite the prayer with the merits of the Mass, it is most powerful:
Eternal Father, I offer Thee the Most Precious Blood Of Thy Divine Son, Jesus, in union with the Masses said throughout the world today, for all the holy souls in Purgatory, for sinners everywhere, for sinners in the Universal Church, those in my own home and within my own family. Amen.