But did he stand against Christ? Being an atheist does not necessarily means being anti Christ. You have forgotten about invinceable ignorance. The Church holds out salvation as possible for everyone, even atheists. Would it be fair to say that God knows the hearts and minds of all souls and judges accordingly. That includes those who pray and if a prayer is directed to a lost soul that God,knowing the heart and mind of the prayor, will direct that prayer to an appropriate recipient? As for those in purgatory, paragraph 958 of the Catechism seems to say they can intercede for us:
"958 Communion with the dead. "In full consciousness of this communion of the whole Mystical Body of Jesus Christ, the Church in its pilgrim members, from the very earliest days of the Christian religion, has honored with great respect the memory of the dead; and ‘because it is a holy and a wholesome thought to pray for the dead that they may be loosed from their sins’ she offers her suffrages for them.“500 Our prayer for them is capable not only of helping them, but also of making their intercession for us effective.”