The phrase “skeleton at the feast” means an element of gloom or depression; an omen of misfortune; a reminder of possible disaster in the midst of pleasure.
The allusion is to a custom in ancient Egypt as related by Plutarch (c. A.D. 46 to 120) in his Moralia.
He tells us that at the conclusion of a feast a household servant carried a mummy into the banquet hall as a reminder to the guests that all men are mortal.
However, our present phrase did not arise in English literature before the middle of the nineteenth century.
It is best known, perhaps, from Long-fellow’s “The Old Clock on the Stairs,” stanza 5:
In that mansion used to be Free-hearted Hospitality;
His great fires up the chimney roared;
The stranger feasted at his board;
But, like the skeleton at the feast,
That warning timepiece never ceased,”Forever, never! Never, forever!”