But, in spite of all his fair promises, Bres, who belonged in heart to his own fierce people, began to oppress his subjects with excessive taxes. He put a tax upon every hearth, upon every kneading trough, upon every quern,as well as a tax of an once of gold upon every member of the the Tuatha Dé Danann. By a crafty trick, too, he obtained the milk of all their cattle. He asked at first only for the produce of any cows which happened to be brown and hairless, and the people of the goddess Danu granted him this cheerfully. But Bres contrived that the ritual bonfires of Bealtaine were placed so close together that when the cattle were driven through for purification, all their hair was singed off. He thus obtained the monopoly of the main source of food.
To earn a livelihood, all the gods, even the greatest, were now forced to labour for him. Ogma, their champion, was sent out to collect firewood, while the Dagda was put to work building forts and castles.
One day, when the Dagda was at his task, his son, Aengus, came to him. You have nearly finished that castle, he said. What reward do you intend to ask from Bres when it is done?
The Dagda replied that he had not yet thought of it. Let me give you some advice said Aengus.Ask Bres to have all the cattle of Ireland gathered upon the Curragh plain, so that you can pick but one for yourself. He will consent to that. Then choose the black-maned heifer called Ocean.
The Dagda finished building the fort, and then went to Bres for his reward. What will you have? asked Bres. I want all the cattle in Ireland gathered together upon the Curragh plain, so that I may choose one of them for myself. Bres did this; and the Dagda took the black-maned heifer Aengus had told him of. The king, who had expected to be asked very much more, laughed at what he thought was the Dagda's simplicity. But Aengus had been wise; as will be seen hereafter.