 Bróðir consulted his brother Óspak , who believed that the signs indicated that much blood would be shed on both sides , that Bróðir 's would all die speedily , that there would be a battle , and all his men would be dragged " down to the pains of hell . " Bróðir was so angered by this that he planned to slay Óspak 's men the next day . Seeing this plan , Óspak deserted his brother during the night with ten ships . He sailed around Ireland to Connaught , and up the River Shannon , to join Brian Boru as an ally . He told King Brian all that he had learned , took baptism , and gathered his men to come to Dublin with Brian 's forces a week before Palm Sunday . 
