The Brynblaidd cannibals (or villagers) were humans who lived in the Welsh country village of Brynblaidd. Every ten years, they would harvest and butcher other humans who would pass by or gotten lost in the countryside. They had done this for countless generations. They were not under any alien or supernatural influence; they did it merely because "it made [them] happy".
One harvest was investigated by Torchwood Three. The team, at the time, suspected alien involvement. The Torchwood team were separated, and Owen, Jack and Gwen were trapped in the inn, while Toshiko and Ianto were captured by the cannibals. Although Tosh managed to escape, and Owen and Tosh rescued Tosh from being strangled, soon four of the five members of Torchwood were captured. Meanwhile, Jack caught one of the cannibals, wounded in the cellar of the inn. He tortured the man into telling him where his friends were being held. As Ianto was about to be bled, Jack crashed into the building with a tractor, and opened fire on the cannibals, overpowering the whole village. (TV: Countrycide)