 The events leading up to the Battle of Clontarf became part of a heroic tale in subsequent tradition , both Irish and Norse , and evil portents were recorded throughout the Norse world . According to Njál 's Saga , one night a great din passed over Bróðir and his men on the Isle of Man , so that they all sprang up from sleep and dressed themselves . Until dawn , this din was accompanied by a shower of boiling blood , which scalded many of them even though they covered themselves with their shields . As a result , " a man had died on board every ship . " On the second night , they awoke to a ghostly assault on their ships by flying swords , axes and spears . Again , this lasted till dawn , and a man died on every ship . On the third night , they were attacked by ravens with iron beaks and claws , once again causing a death in every ship . 
