At a later date, the island became a stronghold of the Mackenzies of Kintail, originally vassals of William I, Earl of Ross. At this early stage, the castle is said to have been garrisoned by Macraes and Maclennans, both clans that were later closely associated with the Mackenzies. Traditional Mackenzie clan histories relate that Earl William sought advantage from the Treaty of Perth of 1266, by which King Magnus VI of Norway ceded the Hebrides to Scotland, and demanded that his kinsman Kenneth Mackenzie return the castle to allow his expansion into the islands. Mackenzie refused, and Earl William led an assault against Eilean Donan that the Mackenzies and their allies repulsed.