Donald II (A.K.A Domnall mac Causantín) was King of the Picts or King of Alba in the late 9th century. He was the son of Constantine I (Causantín mac Cináeda).
Donald was cousins with Constantine who ended up becoming King after his death. The two of them lived for a decade in Ireland in the Royal Court of the Irish King at Grianan of Aileach. Their lives had been endangered after Giric had murdered Constantine’s Father the two young cousins were the most direct threat to Girics throne as Giric was not of Royal blood.
The Royal Court was Gaelic and the cousins left Pictland as Pictish boys but returned as Gaelic Princes.
In 889 AD Donald returned with his cousin Constantine to carry out their revenge on Giric and take the throne. A bloody battle took place at Dundurn in Perthshire, a mighty hill fort with huge fortifications. Giric was slain.
Donald took the kingship of the Picts initially, the date of which is not known but usually placed in 889. He was only King for one year before he was killed. Donald’s reign came with renewed invasions by the Danes, who came less to plunder and more to occupy the lands bordering Scotland and the Anglo-Saxon kingdoms. He was also embroiled in efforts to reduce the highland robber tribes.
It is thought that he was killed in an attack on Donnattar near Stonehaven, Aberdeenshire. It has been suggested that the attack, rather than being a small raid by a handful of pirates, may be associated with the ravaging of Scotland attributed to Harald Fairhair in the Heimskringla. The Prophecy of Berchán places Domnall’s death at Dunnottar, but appears to attribute it to Gaels rather than Norsemen; other sources report he died at Forres. Donalds’s death is dated to 900 by the Annals of Ulster and the Chronicon Scotorum, where he is called king of Alba, rather that king of the Picts. He was buried on Iona.