
1) Irish folklore 2) Tuatha Dé Danann
Found on
https://www.crosswordclues.com/clue/ellén-trechend

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) as having emerged from the cave of Cruachan (Rathcroghan, County Roscommon) and laid Ireland waste until it was killed by the Ulaid poet and hero Amergin. Its name is difficult to interpret: trech...
Found on
http://en.wikipedia.org/wiki/Ellén_Trechend
No exact match found.