He was the son of Gillean of the Battle Axe, and was variously called Maoliosa, or Maol-Iosa, or Gille-Iosa, which means the servant of Jesus.
In 1263, Haakon IV of Norway assembled an expeditionary force, declaring the expedition was intended against that part of Scotland which bordered the western seas, and the object was to revenge certain inroads made by the Scotch into his dominions.
When the expedition arrived at the island of Kerrera, it was joined by King Dugal, predecessor of the MacDougalls of Dunolly, with other Hebrideans.
The king, in person, commanded the center, which was composed of the men from Ross, Perth, Angus, Mar, Mearns, Moray, Inverness, and Caithness.
The High Steward turned the enemy's left, and by an adroit maneuver wheeled back on the rear of Haakon IV of Norway's center, which forced Haakon to retreat from the field, leaving from sixteen to twenty-four thousand of his men on the field, while the Scottish loss did not exceed five thousand.