Battle of Gaine
The Battle of Gaine, a battle in Scottish history, took place over two days in 967 that ended the reign of Duff and ushered in the reign of Culen. The battle is noteworthy for the many members of the Scottish royal family who took part, and for the speed with which Culen's force was able to disembark from the fleet and make its way inland. The battle takes place in the third part of Greg Weisman's short story, "Once Upon A Time There Were Three Brothers...".
Prelude to Battle
After the death of Indulf in Ireland, his son, Culen, plotted to claim the throne of Scotland, which he believed had been stolen from him by Duff's uprising five years earlier. With allies he made during his exile in Ireland, Culen put together an army to invade Scotland and reclaim the throne. Culen sailed up the Western coast of Scotland and land in the rugged highlands in order to attack southeasterly towards the seat of Duff’s court.
As Culen's fleet approached the Point of Ardnamurcan near Wyvern Hill, however, it was spotted by Prince Malcolm and his friend Robbie, who were on an evening ride along the coast.  Upon sighting the fleet, Malcolm and Robbie hurried back to Duff's court to raise the alarm. It is suggested that they were able to make this journey within one night after changing out horses at a field camp.
Despite being spotted at Ardnamurcan, Culen's fleet had achieved its objective of taking Duff by surprise. Duff was forced to march from Edinburgh with a light army, with Prince Malcolm and Kenneth II, to meet Culen's superior force. This sally is notable because it occurred on the very evening that Kenneth III, the heir to Duff's throne, was born; and since he would be too young in practice to take the throne in the event that his father and uncles were killed in battle, the full succession of the family of Maol Chalvim I had marched off to battle at great risk of losing the throne.
Meeting at Gaine
The actual location of Gaine is unknown. What is known, however, is that Duff's army was outnumbered and generally outclassed by Culen's, which had marched deeper into Scotland than had been expected by the Scots when they headed out from Duff's court.
With surprise and numbers on their side, in the first day of battle Culen's army almost brought the Scots to a rout, and Duff was wounded seriously enough that he needed to be carried from the battlefield. Despite the tactical defeat of the Scottish army, Kenneth II displayed great bravery, and Malcolm also is confirmed to have killed an Irish soldier.
During the night before the battle was rejoined, Duff and Kenneth II argued over succession of the throne if Duff should fall, and further over whether or not Duff should participate in the battle due to his wounds. By the end of the night, however, Duff demanded that he remain on the battlefield and that Kenneth II would take the throne if he were to be killed.
On the second day of the battle, Duff was brought onto the field on a litter by four guardsmen. The battle opened with a Scottish rally which and inflicted major casualties on the Irish line. However, one of the guardsmen carrying Duff's litter had been turned by Culen and assassinated Duff at the height of the battle. He was quickly killed by the other guardsmen. Duff's death crushed the morale of the Scottish army and rallied the Irish forces, resulting in a total defeat for the Scottish army, as only Kenneth II, Malcolm, Robert and a few other Scots survived the engagement.
The battle at Gaine was a major strategic victory for Culen. As news of Duff's death and the crushing defeat of his army spread, alliances Duff had made throughout Scotland crumbled and Culen easily took over the kingdom. Kenneth II, the heir to Duff's kingdom, was forced to flee with his family and Robert to northern England in order to regroup for a future invasion to reclaim Scotland. Queen Katharine died from an illness during this retreat.