The Mourioche is a malicious demon in the folklore of French Britanny.
The Mourioche can make himself invisible and transform himself into any animal shape he chooses.
The Mourioche general appearance is a year-old foal.
The Mourioche is especially dangerous to children, and Breton babies are often chided when noisy or mischievous with the words: "Be good, now, the Mourioche is coming!"
Of one who appears to have received a shock, also, it is said: "He has seen the Mourioche." Unlucky is the person who gets in his way; but doubly so the unfortunate who attempts to mount him in the belief that he is an ordinary steed, for after a fiery gallop he will be precipitated into an abyss and break his neck.
In other stories, the Mourioche is seen as a kind of werewolf or a white lady.
Jules Haize. Le Légendaire de la Rance. L'Étang de Beauchêne. Saint-Servan. 1914. Réédition Rue des Scribes. Rennes. 1991.