Duncan is the King of Araluen in the series. He is a popular king, even though he is only in his late thirties. He was married to Rosalind Serenne, but she died shortly after giving birth to his daughter, Cassandra. King Duncan resides in Castle Araluen. He is also one of the best knights in his own kingdom. Halt is one of his main advisers along with Crowley, Geldon, Baron Arald and Battlemaster David. His personal insignia is a leopard. Duncan is described as having light blonde hair and sharp green eyes, traits he shares with his daughter, Cassandra.
The Icebound Land
In The Icebound Land he is publicly insulted by Halt and has to make a choice between death or banishment. Duncan chooses banishment, but bends the rules so that the term is one year, much to the pleasure of Baron Arald and Crowley. He welcomes Halt back three weeks early in The Battle For Skandia (Oakleaf Bearers in Europe), complying with Erak's suggestion of making it a gesture of goodwill to seal the treaty signed between Skandia and Araluen.
At the end of the book he offers Will a place with the Royal Scouts, which Will declines. Duncan offered this position to him presumably because of Cassandra, who has become very close to Will and is saddened at the growing rift between them.
In Erak's Ransom he is given the role of Patron Sponser for Halt and Pauline's wedding. Pauline made up the role on the spur of the moment due to the fact they had no role to give him (which could have been a bit awkward). Anthony, being friends with both bride and groom, adds extra depth to the role by saying that the Patron Sponser must supply the bride and groom with a special (and rather expensive) wedding gift.
The Emperor of Nihon-Ja
The Lost Stories
Death of a Hero
In The Lost Stories he appears in Death of a Hero, which is the first tale in that book. He is leading the battle of Hackham Heath and, the Araluens on the verge of losing, he realizes he needs to send someone to lead the right flank of the army after the main commander, Battlemaster Norman, is mortally wounded. Halt volunteers, which Duncan is pleased with, due to the Ranger's skills in leadership.
The Bridal Dance
He also made an appearance in The Bridal Dance, another story in the book, which tells the story of Evanlyn and Horace's wedding When Will realizes that the Genovesans are planning something that involves the wedding, and he becomes suspicious that King Duncan is a target for assassination.
Later, when the threat of the Genovesan Assassins has been removed and Halt has interrogated one of them, he discovers that the target was in fact Cassandra, not Duncan, for if Cassandra had been killed that would have left Duncan with no direct heir to the throne. That and Yusal's brother wanted her dead.
The Royal Ranger
In The Royal Ranger, Duncan was on the verge of death from an unknown disease. He had a conversation with Halt telling him to look after his daughter.
The name 'Duncan' is the Anglicized form of the Gaelic name Donnchadh meaning "brown warrior", derived from Gaelic donn "brown" and cath "warrior". This was the name of two kings of Scotland, including the one who was featured in Shakespeare's play 'Macbeth' (1606).