While St Patrick is credited with banishing all serpents from Ireland, one is said to have escaped the purge. Lig-na-Paiste — 'the last of the serpents' — survived undetected in a deep pool in the river at Banagher, County Derry, at the edge of the Sperrin Mountains. From its lair, the great serpent laid waste to the surrounding countryside, terrorising communities from the slopes of the Sperrins to the shores of Lough Foyle.
The story
The people eventually turned to Murrough O'Heaney, a local holy man whose church stood in Banagher Glen. St Murrough fasted for ten days and nights, praying for the power to confront the beast. Armed with three rods fashioned from river reeds and divine knowledge of how to trap the creature, he descended to the serpent's pool. Though Lig-na-Paiste begged for mercy, the saint refused, declaring it had sinned against God's people. He bound the serpent in a cage forged by divine power and cast it into the depths of Lough Foyle.
The ruins of Banagher Old Church, where St Murrough worshipped, can still be visited in Banagher Glen. Local tradition holds that Paiste remains coiled and writhing beneath the waters, and that the unusual currents and unpredictable tides of Lough Foyle are caused by the serpent's endless struggle to break free.