What is a Victim Soul?

The Ultimate in "Offering it up": 

A victim soul is someone who's been chosen by God to participate in Christ's Passion in a very special way by manifesting the signs of His sufferings, often in their very bodies. Suffering for the sake of love is their vocation, and such suffering is willingly accepted for the benefit of the Church. The attitude and plea of the victim soul is summed up by this prayer of St. Catherine of Siena:

The only cause of my death is my zeal for the Church of God, which devours and consumes me. Accept, O Lord, the sacrifice of my life for the Mystical Body of Thy holy Church.
St. Lydwine of Schiedam, the Venerable Anne Catherine Emmerich, and St. Pio of Pietrelcina (Padre Pio) were three other such souls, and there have been many more. Often, but not necessarily, these souls receive the stigmata on their palms or feet, the wounds left by the crown of thorns, wounds in their sides as if made by a lance, stripes on their bodies as if caused by scourging, and other bodily phenomena that recall His Passion.