Morcant Bulc inherited the throne of Bryneich in about 580 from his father. Bryneich was a Welsh-speaking dark age kingdom in northern England in approximately what is now the county of Northumberland. The realm existed from the time the Great Northern Kingdom of Coel Hen was divided in c.420 until it's eventual conquest by the Anglo-Saxons in c.600.

Morcant Bulc obtains his bad reputation as "Evil King Morkan" from his almost singlehanded destruction of any hope the Britons of the "Old North" (now northern England) had of resisting the Anglian invaders during 6th Century. He was part of the grand alliance set up by his neighbour, and rival, King Urien of Rheged and which included the support of King Riderch Hael of Strathclyde, the Lords of Gododdin and King Gwallawc Marchawc Trin of Elmet.

The alliance was initially extremely successful in driving back the Angles from Bryneich territory, forcing them to vacate Din Guardi - the capital - in 590 and beseiging them on Ynys Metcaut (now called Lindesfarne). However, Morcant grew envious of the successes of Urien and became uneasy about the prospects of a greatly empowered Rheged after the Angles had been defeated. Treacherously, he had Urien assassinated by a man called Llofan Llaf Difo and the alliance of the Britons of the North collapsed.

Following this a blood feud broke out between Bryneich and Rheged. In the warfare that followed the new king of Rheged, Owain of Rheged was also killed - fatally weakening that kingdom. Meanwhile the Angles had broken out from their containment and retaken most of the lands they had held before the war to expell them had begun. Morcant - now loathed - died shortly after this, having been driven by them into the Cheviot Hills. In the much reduced kingdom he was succeeded by his son Coledauc ap Morcant and then his grandson, although they did not rule long and Bryneich was to be lost within a few years.