St. Gertrude the Great is invoked for souls in purgatory and for living sinners. Our Lord told St. Gertrude that the following prayer would release 1000 souls from purgatory each time it is said. The prayer was extended to include living sinners as well.
“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 family. Amen.”