Many of the icons of Saint John show him with a chalice, and frequently that chalice has a snake emerging from it. The imagery relates to a tale that the evangelist drank from a chalice poisoned by a snake yet was unharmed due to the blessing he gave that potion before drinking it.
The chalice is an important part of this apostles imagery, but I think only partially because of that story. It was John who was with Jesus at the agony of the garden when he said let this cup pass from me, but not my will but thy be done. John was one of the inner circle, witnessing the transfiguration. He stood at the foot of the cross with Mary when Jesus said behold your mother and behold your son. As that chalice held the suffering of Christ that John witnessed at the garden, he also held that vision of the transfiguration. He was in charge of protecting Mary, and of receiving her guidance and wisdom. Mary is that model of the Church, and the one who carried the Christ. Hers was the faith that proclaimed the greatness of the Lord at the incarnation, and the one who maintained that faith throughout Jesus ministry. Hers was the message of Gods joy, and when Jesus said behold your Mother; that joy was placed in charge of John. In a way that chalice that is associated with John is not simply the poisoned cup, but is also that cup of Christ’s suffering, and of the Joy signified through wine.
It is the chalice that contains the messages of Mary, as mother of the Church. It is a symbol, of apostolic succession as the priesthood, and can rightly be looked at as a combined symbol of the ministry Christ’s Church. Johns symbol, that chalice reminds one of that saints ministry role in the Church as a guardian of knowledge, and as teacher. In the Christmas narrative, Jesus is told of being laid in a manger. Later in the story, he will take wine and pour it in a chalice and say this is my blood. That is the chalice that John holds. The Christmas narrative tells of the birth of Christ, Johns story reminds us of the reason. The manger held the body, and the chalice holds the blood.