The Tuatha de Danaan
pre-12th century—present. Old Irish | Modern Irish, folklore.
"He struck himself with a Druid rod that put on him the shape of a pig of the herd, and he began rooting up the ground like the rest."
When the Tuatha de Danaan, the people of the goddess Dana, were the sole human inhabitants of Ireland, they were intermittently at war with the Fomorians who lived over the sea. Once, when the Fomorians had landed on the coast of Ireland, Lugh of the Tuatha de Danaan sent his father Cian to raise men for him to fight the intruders. Cian went north in search of these reinforcements.
Soon he came to a plain in the north of Ireland called the Plain of Muirthemne. Here he sighted three brothers, the three sons of Tuireann, who were the sworn enemies of himself and his own two brothers. Being alone, he decided that to do battle with them was not an option.
Then he saw a great herd of pigs near him, and he struck himself with a Druid rod that put on him the shape of a pig of the herd, and he began rooting up the ground like the rest.
'Did you see a warrior in the distance?' asked Brian, turning to his two brothers. 'It is clear to me what has happened and the reason why we cannot see the man any more,' and he waved his own Druid rod and turned his two brothers into dogs so that they could go and chase out the pig.