Type/Species: Sea Serpent
Origin: Irish Mythology
About Muirdris / Sinach
Muirdris was the earlier name for Sinach, which was later given to the same dragon. Muirdris was a sea creature whose adversary was Fergus mac Leti. Fergus mac Leti met Muirdris in Loch Rury first, where he barely saved his life by running away. His encounter with the creature, however, left his face twisted and ugly. 
So, the nobles attempted to hide this from him by hiding all the mirrors. Finally, however, someone told him about his problem, and he looked at his own face and saw that the monster had done this to him. Fergus then went back into Loch Rury in Country Down and slew the beast. 
While Muirdris is sometimes referred to as a water horse, pictures and other descriptions hold him to be a sea dragon of fearsome proportions. 
For more information on footnotes and references, please see the bibliography.