This fine Welsh Christmas tradition is still kept alive in a few parts of the country. It is a variation on the Wassail Bowl tradition.
It involves taking the skull of a horse, and dressing it with a white sheet, ribbons, and glass for her eyes. During the Festive Season, the Mari Lwyd party would take her from house to house. As they arrived at the house, a singing/riddle competition would take place. First of all, the Mari party would sing a verse of a riddle. The occupants of the house would then have to try to answer the riddle. This would continue until eventually the people inside would not be able to respond. It was nearly always the people inside who failed to answer a riddle, because there were usually more people outside.