Saga - Kenneth MacAlpin, King of Alba

Legend says that Kenneth invited all the Pictish kings to a banquet and murdered them. He killed all the Pictish kings one after another to become King of the Scots and Picts at an unknown point between 839 and 848AD - the historical accounts are rather vague on the exact date. It was Kenneth who named his kingdom Alba. 

Trapped between the ever-threatening Anglo-Saxon kingdom to the south, the Irish wanting to regain a Scottish bridgehead in the west, and growing pressure from a Viking invasion in the north, Kenneth MacAlpin had to take the offensive on every front. He repulsed the Vikings' attacks, fought the Britons of Strathclyde, attacked Lothian (the only Anglo-Saxon part of Scotland), and launched raids against Umbria on the other side of Hadrian's Wall. 

He died of disease around 858, leaving behind a unified Scotland.