a ghost (or spectre) at the feast someone or something that brings gloom or sadness to an otherwise pleasant or celebratory occasion.

☞ The ghost or spectre of Banquo at the feast in Shakespeare's Macbeth is the most famous literary instance of this. There are other versions of the expression. A skeleton at the feast dates from the mid 19th century and probably refers to the ancient Egyptian practice of having the coffin of a dead person, adorned with a painted portrait of the deceased, present at a funeral banquet. A death's head at the feast alludes to the use of a death's head or skull as a memento mori (an object which serves as a reminder of death).