What traditions include "dearly departed" Christians as participants in communion? I've seen some treatments of communion that encourage one to celebrate that their dearly departed relatives are coming up to an invisible railing behind the wall. This seemed to be a great sentiment but I was unclear on what Biblical or catechismal support they were using for this practice.

What Christian traditions specifically teach this sort of including the departed in communion? Is this practice something common to all Christian sects that profess a "real presence" of Christ in communion (i.e. does it have a place in the Catholic catechism, Presbyterian Common Book of Prayer, Book of Concord, etc.?) or is it isolated to a more specific doctrinal tradition? Can anyone trace the origin of this tradition?
Catholic's believe that each time Mass is celebrated it is done with the entire Communion of Saints. it would just be ones imagination at work seeing dead relatives at Communion, but in effect I think that is what Catholics believe.

To the offering of Christ are united not only the members still here on earth, but also those already in the glory of heaven. In communion with and commemorating the Blessed Virgin Mary and all the saints, the Church offers the Eucharistic sacrifice. In the Eucharist the Church is as it were at the foot of the cross with Mary, united with the offering and intercession of Christ.
CCC 1370

and one of the names for the Eucharist (Communion) comes from the &quot;Communion of Saints&quot;

Holy Communion, because by this sacrament we unite ourselves to Christ, who makes us sharers in his Body and Blood to form a single body. We also call it: the holy things (ta hagia; sancta) - the first meaning of the phrase &quot;communion of saints&quot; in the Apostles' Creed - the bread of angels, bread from heaven, medicine of immortality, viaticum.
CCC 1331

So that takes care of the Church Triumphant, but the Church Suffering (the Holy Souls in Purgatory) can also be remembered and had the Sacrifice of Mass offered for their salvation

The Eucharistic sacrifice is also offered for the faithful departed who &quot;have died in Christ but are not yet wholly purified,&quot; so that they may be able to enter into the light and peace of Christ:
CCC 1371

I believe Orthodox Christians believe the same thing since this is not a point of contention between the churches.