The Ellén Trechend is a three-headed monster referred to in Irish mythology. It is mentioned in the text Cath Maige Mucrama (The Battle of Mag Mucrima)...

Cat-sìth Cù-sìth Changeling Clíodhna Clurichaun Dobhar-chú Dullahan Ellén Trechend Fachan Far darrig Fear gorta Am Fear Liath Mòr Fetch Fuath Gancanagh...

Chulainn. He had two other sons, Condra and Amergin. He killed the Ellén Trechend, the three-headed monster that made raids on Ireland from the cave of...