There are no wolves in Ireland today, but in the early medieval period, they roamed the country and terrified people. The time was ripe for the legend of Laignech Fáelad, who was a brother of Feradach mac Duach, the king of Ossory. Laignech Fáelad had the power, and the habit, of "going wolfing," meaning he would turn into a wolf and roam the fields, killing and eating the herds. His offspring, who inherited the trait, would accompany him on this nighttime raids.
The descendants of Laignech Fáelad retained the name as a tribe, and had a fearsome reputation of fighting like wolves. They were said to be mercenaries, and whichever king could pay them could wield an overwhelming force against their enemies. However, they required payment in infants, which they would devour.
The Laignech Fáelad are mentioned several times in medieval chronicles, with some variation in details. It was said that when St. Patrick preached the Gospel to the Irish, the Laignech Fáelad would howl like wolves trying to drown him out. -via Strange Company