The term 'Holy Vessel' can be summarized as a reference to the GRAIL, a legendary object associated with the Arthurian legend. The GRAIL is a cup or dish that is said to have been used by Jesus at the Last Supper and is believed to possess miraculous powers. It is also associated with the quest for the Fisher King, a figure from the Arthurian legend. The GRAIL has been a popular subject of literature, art, and film throughout the centuries.