Some souls in purgatory don't have anyone to pray for them.
For Catholics, the concept of purgatory is a consoling thought, knowing that anyone who reaches this final stage of purification can only go “up.”
However, it is also a belief that those souls in purgatory benefit from our prayers, which somehow shorten the time they spend in purgatory. This stage of the afterlife is still a mystery to us, but we try to understand it from various passages in the Bible as well as the teaching of the Church.
Whatever the case may be, in our charity, we can also direct our prayers to souls most forgotten by those on earth, asking God’s mercy to be showered upon them.
Here is a prayer from the Raccolta that directs our prayers to that soul in most need of our prayers.
O Lord God Almighty, I pray Thee, by the Precious Blood which Thy Divine Son Jesus shed in the garden, deliver the souls in purgatory, and especially that soul amongst them all who is most destitute of spiritual aid; and vouchsafe to bring it to Thy glory, there to praise and bless Thee for ever. Amen.