In 1044 , the Annals of Tigernach record that Ímar penetrated into the domain of the Uí Fhíachrach Arda Sratha and killed their chief . The annal @-@ entry also indicate that Ímar stormed the church of Armagh , and burned Scrín Pátraic ( the " Shrine of Patrick " ) in the attack . The following year , he again invaded Rathlin Island , and his subsequent slaughter of three hundred noblemen of the Ulaid , including a certain heir apparent named Ragnall Ua Eochada , is documented by the Annals of Clonmacnoise , the Annals of Inisfallen , the Annals of Tigernach , and the Annals of the Four Masters . This remarkable action may indicate that the Dubliners and Ulaid was battling for control of Rathlin Island . If so , it could be evidence that Ímar enjoyed the possession of Mann by this date . The domain of the Ulaid is certainly the closest Irish territory to Mann , and the control of the Manx fleet could account for the Dubliner 's ability to challenge the Ulaid . Whatever the case , within the year Niall mac Eochada , King of Ulaid ( died 1063 ) is recorded to have attacked Fine Gall — Dublin 's agriculturally @-@ rich northern hinterland — in what may have been a retaliatory raid .