Dictionary of National Biography, 1885-1900/Donald VI
DONALD VI (d. 900), son of Constantine I [q. v.], king of Celtic Scotland, succeeded Eocha and Grig (Gregory), who had reigned jointly, the latter, perhaps, being the representative of the northern Celts or Picts and the former a son of Run of the British race, but by his mother a grandson of Kenneth Macalpin. His reign, when the kings of Scone are first called kings of Alban and no longer of the Picts by the Irish annalists, was during the period of the great Danish Vikings, who now began to settle in instead of ravaging the coasts. Guthorm Athelstan about this period, defeated by Alfred, became a christian and settled in the eastern district called the Danelege. Halfdene, who commanded the northern half of the formerly united Danish host, attacked and settled in Northumbria. The Celts in Ireland succeeded in repelling the Danish invaders till 919, when Sitric, by their defeat at Rathfarnham, laid the foundation of the Danish kingdom of Dublin. Another band of northern Vikings, led by Hrolf (Rollo), sought the more distant shores of Normandy. Meanwhile Harold Harfagr was consolidating the kingdom of Norway, and a little later Gorm the old that of Denmark.
The less fertile Scotland had a short period of comparative quiet. Donald is said by Fordun to have made peace with Ronald and Sitric, his kinsman, the successors of Guthorm, Danish chiefs not clearly identified (Scotichronicon, iv. 20).
Sigurd, brother of Ronald, earl of Moire, the second earl of Orkney, indeed invaded northern Scotland and took possession of Caithness, Sutherland, Ross, and Moray, according to one account, as far as Ekkiallsakki (Burghhead, between the Findhorn and Spey), where he defeated Melbrigda Tönn (the Tooth), but died from a wound of the tooth of his defeated foe's head slung over his saddle, according to the Norse Saga. But this north-eastern part of Scotland had probably never been under the Celtic kings of Scone. According to the narrative of ‘The Wars of the Gaedhill with the Gael’ (Todd's edit. p. 29) a later attack, led by Sitric, son of Imhair, came further south, defeated the Scots, and (Skene, i. 338) slew Donald at Dun-fother (Dunottar) in Kincardine. But the Ulster annals, as well as the earliest Scottish historians, ignore this invasion, and record the death of Donald about 900, according to Fordun, at Forres, not in battle but from infirmity, brought on by his labour in reducing the highland robber tribes, though Fordun adds a doubt whether he may not have been poisoned. He was succeeded by Constantine, the son of Aedh the predecessor of Gregory.
[Wyntoun and Fordun; Wars of the Gaedhill and Gael; Annals of Ulster; and for modern accounts see Skene's Celtic Scotland, i. 335, and Robertson's Scotland under her Early Kings, i. 50.]