After the murder in 1095 of his half-brother, Duncan II, who had reigned for less than a year, the twenty-year-old Edgar claimed the Scottish throne for himself. However, he did not have enough support from other nobles, Eventually, in 1097, with the support of William II of England, he managed to defeat his uncle, Donald III, and elder brother Edmund, to secure the throne. Not a great deal is known about his reign, but we do know that the following year he signed a treaty with the Norwegian king Magnus Barefoot, recognising the Norwegian possession of the Hebrides and Kintyre.
Editors. "Reign of King Edgar of Scotland". The Literary Encyclopedia. First published 31 July 2012
[http://www.litencyc.com/php/stopics.php?rec=true&UID=613, accessed 25 November 2015.]