There were two Vikings from the Southern Isles, named Vigbjod and Vestmar; they were abroad both summer and winter. They had eight ships, and harried mostly round the coast of Ireland, where they did many an evil deed until Eyvind undertook the defence of the coast, when they retired to the Hebrides to harry there, and right in to the Scotch firths. Thrand and Onund went out against them and learned that they had sailed to an island called Bot. Onund and Thrand followed them thither with five ships, and when the vikings sighted them and saw how many there were, they thought their own force was sufficient, so they took to their arms and advanced to the attack. Onund ordered his ships to take up a position between two rocks where there was a deep but narrow channel, open to attack from one side only, and by not more than five ships at once. Onund was a very wily man. He sent his five ships forward into the channel so that, as there was plenty of sea room behind them, they could easily retire by merely backing their oars. One ship he brought under an island lying on their beam, and carried a great stone to a place on the front of the rock where it could not be seen from the enemy's ships. The Vikings came boldly on, thinking they had caught them in a trap. Vigbjod asked who they were that he had hemmed in. Thrand answered that he was a brother of Eyvind the Easterner, and the man with him was his comrade, Onund Treefoot. The vikings laughed and said:

Never yet did I see men go to battle who could not carry themselves."

Onund said that could not be known until it was tried. Then the ships came together. There was a great battle in which both sides fought bravely. When the battle was thick Onund ordered his ships to back their oars. The vikings seeing it thought they were taking to flight, and pushed on with all their might, coming under the rock just at the moment when the party which had been dispatched for that purpose arrived. They launched upon the vikings stones so huge that nothing could hold against them. A number of the vikings were killed, and others were so injured that they could fight no more. Then the vikings tried to escape, but could not, as their ships were in the narrowest part of the channel and were impeded both by the current and by the enemy's ships. Onund's men vigorously attacked the wing commanded by Vigbjod while Thrand engaged Vestmar, but effected little. When the men on Vigbjod's ship had been somewhat reduced, Onund's men, he himself with them, prepared to board her. On seeing that, Vigbjod spurred on his men resolutely. He turned against Onund, most of whose men gave way. Onund was a man of immense strength and he bade his followers observe how it fared with them. They shoved a log under the stump of his leg, so that he stood pretty firm. The viking dashed forward, reached Onund and hewed at him with his sword, which cut right through his shield and into the log beneath his leg, where it remained fixed. As Vigbjod bent down to pull his sword clear again, Onund dealt him a blow on his shoulder, severing his arm and disabling him. When Vestmar saw his comrade fall, he sprang on to the outermost ship and escaped along with all who could get on to her. Then they examined the dead. Vigbjod had already expired. Onund went up to him and said:

They took a large quantity of booty and returned to the Barra Isles in the autumn.