There is an old abbey on the river, in County Mayo, and people say the fairies had a great battle near it, and that the slaughter was tremendous. At the time, the fairies appeared as swarms of flies coming from every direction to that spot. Some came from Knock Ma, and some from South Ireland, the opinion being that fairies can assume any form they like. The battle lasted a day and a night, and when it was over one could have filled baskets with the dead flies which floated down the river. (Evans-Wentz, 1911, 39)