This folktale from Lough Derg tells the tale of the local Peistha, which was destroyed by St. Patrick.
In the old Pagan times, a Peistha, or water serpent, of immense girth and of still greater trail was believed to haunt the celebrated Lough Derg. His horrid head and open jaws were sometimes seen above the surface, as if drawing in the upper air, but more often it was seen gliding slowly through the depths.
When St. Patrick landed at Saints’ Island, the Peistha had already destroyed many dwelling on the banks. The saint could not tolerate the presence of such a monster. With a mighty stroke of his staff, the Peistha was destroyed. The waters of the Lough soon began to assume a reddish tinge, so freely did the monster bleed. And so it received a new name — the Red Lake.
The skeleton of the Peistha remained on Station Island to the beginning of the nineteenth century. Many of the old people living around the shores at that time claimed to have conversed with persons who alleged they saw the last remaining portions of that serpent’s body moldering into dust.
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