Hanged, drawn and quartered for treason by the English.
Christopher and his brothers John and Humphrey de Seton were the sons of Sir John de Seton of Skelton, Cumberland and this branch of the Seton family had long served the Bruces in Yorkshire, Cumberland and Scotland. The family have no connection to Alexander Seton (Governor of Berwick) that has been discovered.
Christopher married Robert de Brus's sister Christian or Christina Bruce about 1300. Christian was thought to have married as her first husband Gartnait, Earl of Mar, but this is incorrect.
Sir John Comyn of Badenoch was stabbed but not killed by Robert de Brus in Greyfriars Church on 10 February 1306. In the melee, Sir Christopher struck down Sir John's uncle, Sir Robert Comyn. There has long been a tradition at Dumfries of the Comyns being killed in two stages. A letter of excommunication was issued naming the Earl of Carrick and three other knights, Sir Alexander Lindsay, Sir Christopher and his brother John Seton as John Comyn's murderers.
Christopher was present at the coronation of his brother in-law King Robert I, King of Scots, at Scone on 25-26 March 1306. He is erroneously thought to have been present at the Battle of Methven on 19 June 1306 but Duncan clears the point up by placing his at Loch Doon Castle, an important castle for the Earls of Carrick and one of three that Robert tried desperately to hang on to, but Loch Doon fell about 14 August.
Loch Doon Castle, Ayrshire, was besieged by the English and after the surrender of that castle by the Governor Sir Gilbert de Carrick, Christopher was hanged at Dumfries as a traitors of King Edward I of England. His Cumberland estates, with the exception of his mother's dower, were given to Sir Robert de Clifford. A small chapel was raised by his wife Christian, at Dumfries to the memory of her husband in 1326 (wikipedia)