Sister Faustina Kowalska, the Polish nun who had mystical encounters with the merciful Christ in the early 20th century, was canonized a saint by Pope John Paul II. The Pope also declared the first Sunday after Easter to be Divine Mercy Sunday, and it was during the vigil Mass of this feast that the Holy Father received his last Holy Communion and drew his last breath. The message of Divine Mercy as communicated through Sister Faustina is...