[6] This maternal descent from the royal Alpínid dynasty may well account for the record of Eochaid reigning over the Pictish realm after the death of Cináed's son, Áed, in 878.
According to various sources, Áed was slain by Giric, whose ancestry is uncertain and who then proceeded to usurp the Alban throne.
Heir to the Brythonic kingdom of Strathclyde and a claimant to the Gaelic throne of the Picts, Eochaid was of mixed blood.
Whilst it is possible that they held the Pictish kingship concurrently as allies, it is also conceivable that they ruled successively as opponents.
A daughter of Eochaid may have been Lann, a woman recorded to have been the mother of Muirchertach mac Néill, King of Ailech.
[19] In the following year, Amlaíb and Ímar returned to Ireland with a fleet of two hundred ships, and a mass of captives identified as English, British, and Pictish.
[21] The Annals of Ulster[22] and Chronicon Scotorum reveal that he was slain at the behest of Rhun's brother-in-law, Custantín mac Cináeda, King of the Picts.
[23][note 4] The circumstances surrounding Arthgal's assassination are unknown,[25] and Rhun's reign probably commenced not long after his death.
[47] Whilst the Annals of Ulster reports that Áed was killed by his own companions,[48] several mediaeval king-lists state that he was slain by a certain Giric.
[50] According to the Chronicle of the Kings of Alba, Eochaid succeeded Áed and held the kingship for eleven years.
[68] The chronicle's inconsistency in regard to the eclipse may owe itself to an attempt to increase the dramatic effect of the regime change by associating a remarkable astronomical event with Eochaid's expulsion.
[70] According to the latter, Eochaid ruled as king for thirteen years until he was expelled and succeeded by Giric (described as "the son of fortune").
[77] Giric need not have possessed any claim of his own,[78] and could have merely played the role of kingmaker, by orchestrating the removal of Áed, and installing Eochaid in his place.
[87] Such a relationship could indicate that Giric's apparent killing of Áed was undertaken in the context of avenging Arthgal's demise at Custantín's behest.
[106][note 12] The remarkable uncertainty surrounding the Pictish kingship during this period means that it is also possible that Eochaid and Giric were rivals rather than allies.
[111][note 13] At some point after the loss of Al Clud, the Kingdom of Strathclyde appears to have undergone a period of expansion.
[115] Although the precise chronology is uncertain, by 927 the southern frontier appears to have reached the River Eamont, close to Penrith.
[120][note 15] Amiable relations between these powers may be evidenced by the remarkable collection of contemporary Scandinavian-influenced sculpture at Govan.
[130] In fact, the shifting terminology employed by various English, Irish, and Scottish sources may be evidence that the Pictish realm underwent a radical transformation during this period in history.
For instance, it is conceivable that Giric gained the throne by seizing upon the upheaval caused by the incessant Viking depredations that assailed Pictavia.
At an earlier date, the Gaelic realm of Dál Riata appears to have crumbled under such pressures, and it is possible that Giric drew military power from this broken polity to forcefully seize the Pictish throne.
In any case, the accommodation of significant Gaelic aristocratic power in the wavering Pictish realm could account for the eventual transformation of Pictavia into Alba.
[148] If Domnall and his succeeding first cousin, Custantín mac Áeda, indeed spent their youth in Ireland prior to assuming the kingship of Alba, their Gaelic upbringing could well have ensured the continuation of Pictavia's Gaelicisation.
[151] Several king-lists allege that Giric subjugated Ireland and England during his reign,[152] an outlandish claim that could instead evince a multi-ethnic northern alliance under his authority.
[161] Unlike Giric, later mediaeval king-lists and chronicles fail to include Eochaid within their accounts of Scottish history.
[163] The window within which Eochaid and Giric appear to have reigned marks the only point between the careers of Cináed and Máel Coluim mac Cináeda, King of Alba that a patrilineal Alpínid is not known to have ruled the Pictish/Alban realm.
[185] Eochaid may have also had a daughter, Lann, the wife of Niall Glúndub attested by the Great Book of Lecan version of the twelfth century Banshenchas.