Type/Species: Sea Serpent
Origin: Irish Folktale
About Ollipeist / Ollepheist / Ollipheist / Uilepheist
Ollipeist's name is from the Irish Gaelic words oll, meaning "great," and peist, meaning "fabulous beast." People described him as a huge dragon, vast and strong, inhabiting a lake in Ireland. 
When Ollipeist heard that St. Patrick, the bane of the snakes of Ireland, planned to remove him from his own lake, the otherwise benign dragon became completely enraged.  Just at that moment, a drunken piper named O'Rourke (or O Ruairc) passed near the dragon, and in his fury, Ollipeist swallowed the man.  To the dragon's chagrin, O'Rourke kept on drunkenly playing inside the monster's belly, giving him an upset stomach and annoying him at the same time. Finally, Ollipeist vomited O'Rourke back up,  and escaped St. Patrick by leaving Ireland in quite a rush. 
St. Patrick's emblems are the snake and the shamrock, for it is said that he banished all the snakes from Ireland. 
He also chased the dragons away, and as Ollipeist left Ireland, his tail carved the Shannon Valley. 
Ollipeist originally lived quietly and benignly in Ireland before St. Patrick threw him out. His story is allegorical for the changing impression of serpents and dragons in Irish Folklore and Legend with the integration of Christianity to the region.
For more information on footnotes and references, please see the bibliography.