Eucharist
The Eucharist, also known by other names such as the Holy Communion, the Lord's Supper, or Mass, is a religious ritual for Christians in which, during church, the members eat bread (usually a thin, circular disk called a wafer) and drink wine (or sometimes water or grape juice as a replacement). The members partake in this sacrament because, according to the bible, at the Last Supper, Jesus gave his disciples bread and wine and told them to eat and drink those. He told them that the bread is his body, and the wine is his blood. However, despite this being a sacrament for most Christians, due to the existence of the various denominations which exist under the general category of Christianity, the different groups have disagreements concerning the Eucharist. Most of the denominations agree that the Eucharist contains the presence of Jesus, but they disagree on how, when, and where. Some groups believe that the bread and wine are actually Jesus' flesh and blood while others think that they are only symbols of Jesus' body. There are also denominations who believe that the bread and wine undergo transubstantiation (they change into Christ's flesh and blood). One other difference between the factions is where the Eucharist should be available to all Christians or whether there should be requirements for those who want to participate in Communion (such as the Baptists who restrict this sacrament for those who were baptized properly). Regardless of these differences, the majority of the denominations agree that the Eucharist deepens the relationships between the participants and Christ.
In Relation to the Holy Grail:
In the Arthurian universe (particularly in the universes illustrated in the stories with more religious ties), the knights attend Mass. Usually, their attendance is a minor detail that is briefly mentioned before they start their journey for the day, but the knights' diligence in going is important. For example, Galahad​, in The Quest for the Holy Grail, goes to Mass as often as possible because he is a pious and devoted individual. In addition, there are ties between the Holy Chalice, which Jesus used for wine in the Last supper, and the Holy Grail, which is a significant item that knights embark on quests for in Perceval, or the Story of the Grail; The High Book of the Grail (Perlesvaus), Parzival and Titurel, and a myriad of other stories. Despite the discrepancies between the background of each object (the Holy Chalice being used for drinking wine at the Last Supper and the Holy Grail for holding Jesus' blood from his crucifixion), there is a similarity in that both contain, symbolically or physically or both, Jesus' blood.
