Nella mitologia irlandese, Tethra dei fomoriani regnò su Mag Mell dopo la morte nella seconda battaglia di Mag Tuiredh.[1] Dopo la battaglia la spada di Tethra, Orna, viene recuperata da Ogma e gli racconta tutte le imprese compiute.[2]
Now in that battle, Ogma the champion found Orna, the sword of Tethra, king of the Fomoire. Ogma unsheathed the sword and cleaned it. Then the sword told what had been done by it, because it was the habit of swords at the time to recount the deeds that had been done by them whenever they were unsheathed.