Although Owain ap Hywel Dda lived until 988, he had turned over active rule of his kingdom to a son, Einion, about 975....
Einion, as acting king, was engaged in defending Deheubarth from both Saxon raids and from the leading men of Gwent; the latter probably battled over Gower, lands which had once been attached to Gwynlliw before the latter was incorporated into Glamorgan. The Gwent brothers, Hywel and Iestyn ap Owain ap Morgan Hen, killed Einion in battle in 984 while his father was yet living, so he never became king in his own right. 1
The Chronicle of the Princes records Einion assisting King Iago of Gwynedd in driving the Irish and their Danish allies from Wales in 966. Einion then raided Gower again the next year, "on the pretense" of opposing the pagan Vikings and their supporters. This prompted a retaliatory raid by King Owain of Morgannwg, who brought Gower back under his control, and an invasion by King Edgar of England, who forced Einion's father Owain to swear fealty to him at Caerleon upon Usk. A third raid in 976 went little better: Einion is recorded devastating the area so thoroughly it provoked famine but Owain ap Morgan's brother Ithel defeated him and restored the plunder to its owners. At some point, he seems to have annexed Brycheiniog for Deheubarth and King Hywel of Gwynedd—with the support of Ælfhere of Mercia—then invaded in 980 and 981. Einion defeated them at Llanwenog and in Brycheiniog but the country was heavily despoiled by the northerners and the English and by a Viking raid against St. David's in 980 or 982.
Einion predeceased his father, being slain at Pencoed Colwynn by the men of Glywysing and Gwent in AD 982 or 984.His offices were taken by his brother Maredudd, rather than by either of his sons. His line recovered the throne under his grandson Hywel around 1035.
He is sometimes credited with being the namesake of Port Eynon or Einon on the Gower peninsula. 2