It is best known for St Patrick's Purgatory, a site of pilgrimage on Station Island in the lake.

Generally, pilgrims depart on the morning of the third day having slept on their second night.

The worm then grew into a large monster called Caoránach that devoured the local cattle.

Once a majority of the cattle in Ulster died the locals blamed Conan who then enraged attacked the beast, killing it.

Its blood dyed the rocks red and this is where the name Lough Derg comes from.