Holy Grail
The Holy Grail refers to a specific chalice that belonged to Grand Admiral Thrawn of the Chiss in the year 2 BBY. This item was kept within his office located on the Chimaera.
Behind the scenes
Within the context of real-world religious studies, the Holy Grail is traditionally understood to be the very cup that Jesus Christ used at the Last Supper. The inclusion of the Holy Grail in Star Wars Rebels served as an allusion to the 1989 movie Indiana Jones and the Last Crusade, where the Holy Grail functioned as the central MacGuffin.