The Holy Grail is a sacred object

Relic

In religion, a relic is a part of the body of a saint or a venerated person, or else another type of ancient religious object, carefully preserved for purposes of veneration or as a tangible memorial...

 figuring in literature and certain Christian traditions, most often identified with the dish, plate, or cup used by Jesus

Jesus

Jesus of Nazareth , commonly referred to as Jesus Christ or simply as Jesus or Christ, is the central figure of Christianity...

 at the Last Supper

Last Supper

The Last Supper is the final meal that, according to Christian belief, Jesus shared with his Twelve Apostles in Jerusalem before his crucifixion. The Last Supper provides the scriptural basis for the Eucharist, also known as "communion" or "the Lord's Supper".The First Epistle to the Corinthians is...

 and said to possess miraculous powers. The connection of Joseph of Arimathea

Joseph of Arimathea

Joseph of Arimathea was, according to the Gospels, the man who donated his own prepared tomb for the burial of Jesus after Jesus' Crucifixion. He is mentioned in all four Gospels.-Gospel references:...

 with the Grail legend dates from Robert de Boron

Robert de Boron

Robert de Boron was a French poet of the late 12th and early 13th centuries who is most notable as the author of the poems Joseph d'Arimathe and Merlin.-Work:...

's Joseph d'Arimathie (late 12th century) in which Joseph receives the Grail from an apparition of Jesus and sends it with his followers to Great Britain

Great Britain

Great Britain or Britain is an island situated to the northwest of Continental Europe. It is the ninth largest island in the world, and the largest European island, as well as the largest of the British Isles...

; building upon this theme, later writers recounted how Joseph used the Grail to catch Christ's blood

Blood of Christ

The Blood of Christ in Christian theology refers to the physical blood actually shed by Jesus Christ on the Cross, and the salvation which Christianity teaches was accomplished thereby; and the sacramental blood present in the Eucharist, which is considered by Catholic, Orthodox, Anglican, and...

 while interring him and that in Britain he founded a line of guardians to keep it safe.