Crom Cruach, the Master of the Runes, and the Bloody Crooked One, was a deity in pre-Christian Ireland, reputedly propitiated with human sacrifice, whose worship is said to have been ended by St. Patrick. Crom Cruach's cult image, consisting of a gold figure surrounded by twelve stone figures, stood on Magh Slécht ("the plain of prostration") in County Cavan, and was propitiated with first-born sacrifice in exchange for good yields of milk and grain.
Crom is said to have been worshipped since the time of Érimón. An early High King, Tigernmas, along with three quarters of his army, is said to have died while worshipping Crom on Samhain eve, but worship continued until the cult image was destroyed by St. Patrick with a sledgehammer. It is revealed that it is in fact a Great Old One, posing as a pre-Christian deity in order to gain the souls of children, whilst deceiving those whom offer it with the sacrifices, the milk and grain revealing to have components which causes the folks to slowly become Elditrch monstrosities, and under its command.