"Triple-headed Aillén." A triple-headed monster mentioned in the text Cath Maige Mucrama ("The Battle of Mag Mucrima"). It lived in a cave called Oweynagat at Cruachain, County Roscommon. The monster, described as sometimes male, sometimes female, emerged from its cave on the eve of Samhain to lay waste to the land. It was particularly hostile toward the hill-fort Emain Macha (County Armagh) and the Hill of Tara (County Meath). It was slain by the warrior-poet Amairgin mac Eccit.
- MacKillop, James. (2004). Dictionary of Celtic Mythology. New York: Oxford University Press, Inc.