It’s March, and for many that means shamrocks, leprechauns, green beer, corned beef and cabbage. All these things are related to the ceebration of Saint Patrick, the fifth-century Romano-British Christian missionary and the primary patron saint of Ireland. His Christian name is believed to be Maewyn Succat, born in 387 A.D. in modern-day Great Britain, which at the time was still part of the Roman Empire. There are many legends associated with Saint Patrick, including using the shamrock to teach the concept of the Holy Trinity, as well as thrusting his walking stick into the ground while evangelizing before having it spout into a living tree.
However, one of the more intriguing of all the oral traditions surrounding Saint Patrick holds that while attempting to fast for 40 days he was attacked by a group of snakes. In self-defense, he chased all the snakes away, exterminating them permanently from the region. It has never been scientifically or ecologically proven that St. Patrick rid Ireland of snakes, and scholars have other theories about why snakes might not inhabit the country, but this legendary tale is linked to a truly terrifying sea serpent-like monster from Irish mythology known as the Oilliphéist.
The name Oilliphéist is derived from the Gaelic-Irish words “oll” meaning great, and “péist” meaning worm, monster, or reptile. According to Irish oral tradition, these monsters inhabit the lakes and rivers in Ireland. Not only is the Oilliphéist extremely large and up to 200 feet long, but the serpentine-shaped creature is said to have a venomous breath that could poison the land.
It has scaly and rough skin, a dark green or black color and large, sharp teeth that protrude from its mouth. It has eyes that glow red in the dark, and some accounts also describe it as having a mane of hair or fur along its spine.
According to legend, despite its destructive power and massive size, when this serpent- dragon became aware of Saint Patrick’s plan to banish the snakes from Ireland, it made its escape before Saint Patrick arrived. In its hasty retreat, the Oilliphéist’s formidable body cut a long, deep scar through the land that became the mighty River Shannon, the longest river in the British Isles.
Given this body of water’s fabulous creation story, it’s no wonder that today the Shannon reputedly hosts a river monster of its own known as a Cathaigh, or Cata for short. The mysterious creature is said to dwell by an island in the Shannon Estuary, off the coast of Kilrush in Clare. Cata is regarded as this islands protector, placed there by supernatural design to ensure no one set foot on what was a holy island. The creature is said to have killed all that came to its island. So feared is the creature that the island was named Inis Cathaigh which translates to ‘The island of Cata.’ Like the fabled Loch Ness Monster, over the centuries the fantastical beast has reportedly been sighted on numerous occasions.
Cata is described as a hideous, ruthless beast with a horse’s mane, gleaming eyes, and two hideous, thick feet with nails hard as iron. Cata has fiery breath, a belly like the bellows of a furnace, a whale’s tail with hard, rending claws.
Saint Patrick is associated with still another mythological water beast.
Caorthannach (sometimes Caoránach), according to legend, is a terrifying creature born at the beginning of time that is said to be the mother of demons, and even the mother of the Devil himself.
After Saint Patrick cleansed the island of snakes, whisking them away in a whirlwind and banishing them beyond the sea, Caorthannach retaliated against the Saint and a battle ensued. It is said they fought for two days and two nights before the Caorthannach slipped down from the mountain to retreat to the safety of Lough Derg. Patrick is said to have pursued the creature, all the while Caorthannach spit fire into rivers and wells to prevent Saint Patrick from drinking pure water.
The tale ends with Saint Patrick falling to the depths of the lake with Caorthannach, where the monster eats him before he slices the monster’s belly open to escape.
The blood flowing from the defeated monster caused the water to turn red, prompting Saint Patrick to declare that the lake be called Lough Dearg, which translates to red lake.
In a variant of this tale, Saint Patrick does not kill the monster, instead he knocks Caorthannach into the lake and banishes it to remain in an underwater cave where it lives on to this day.
I hope you found this information about Saint Patrick’s association with these legendary creatures interesting, giving horror and cryptid fans a little something extra to appreciate this month, and on March 17 in particular.
Happy Maewyn Succat Day!
Published 3/3/25