Around 881, Viking jarlskona Eivor Varinsdottir visited the settlement of Aileach, under the pretense of a Viking from Donegal. Under Flann's orders, Eivor had to investigate what the situation was with the Kings Domnall and Niall and her cousin, Bárid mac Ímair, King of Dublin. Upon her arrival, Eivor saw the Kings Niall and Domnall and her cousin, drunk, as the kings asked her why she traveled to Aileach. Meanwhile, Bárid and Eivor spoke in coded messages within their conversation with the kings as she lied, saying she was invited. From the conversation with the kings, Eivor was allowed by King Domnall to wait as they find out why she was summoned to them. As Bárid kept the kings busy, Eivor released the prisoners and took over Aileach with the prisoners' help.
Bárid took the kings as hostages as Eivor entered back into the kings' room. Both Eivor and Bárid questioned the kings of their actions, where Domnall admitted to being told by the Abbot Eogan mac Cartaigh. Not knowing the size of Eogan's army, King Domnall revealed that Eogan pressured him and King Niall to make sure Flann doesn't check out the area of Aileach. Both Kings Niall and Domnall admitted that Eogan was building an army to march to Clogher. Warranting a need of alert, Bárid sent a message to King Flann about the upcoming attack, while he dealt with Kings Niall and Domnall as his hostages.
Around 882, after the defeat and death of the Ollamh Druid, Abbot Eogan, King Domnall was one of the kings of Ireland of a meeting in Durrow that summoned High King Flann. In the meeting, an initial decision was made to enforce a druid inquisition after the recent events with Eogan and the Children of Danu. This decision was highly opposed from Flann's poetess, Ciara ingen Medba, who stormed out, while King Domnall and the other kings were in favor of the decision.
Behind the scenes
Domnall is a historical character in Assassin's Creed: Valhalla's Wrath of the Druids DLC. Historically, Domnall only ascended to the throne of Ailech in 887 after succeeding two previous kings after the death of Áed Findliath, while his brother Niall Glúndub did not rule with him until 896. In the events of the DLC which takes place between 879 and 882, Domnall and Niall are portrayed as co-kings of Aileach.