A druid with supernatural powers killed by Manannán mac Lir. Fer Fidail was either the son or grandson of Eógabal and related to Fer Í. When Manannán became smitten with the beautiful Tuag, he was frustrated to find she was kept under constant guard by hosts of women. He asked Fer Fidail to enter her chamber, which he did, dressed as a woman. He remained with her for three nights and, after singing a sleep-inducing song over her, left her slumbering on the shore of Inber Glas (the mouth of the Bann River) while he looked for a boat. Suddenly a wave came to drown her, a wave identified in some versions as Manannán himself. For allowing Tuag to perish, Fer Fidail himself was killed, although the context implies that Manannán's jealousy was the greater cause. See also FER Í.