That same year, the neighbouring king of Osraige Cerball mac Dúnlainge, who had repeatedly attacked Leinster over the previous decades in an attempt to make it subject to him, died.
In 902 they state that he, together with Máel Finnia mac Flannacain of Brega lead an expedition to Dublin which drove the "foreigners", the Vikings and Norse-Gaels, from Ireland.
He fought alongside Flann (whose daughter Gormflaith ingen Flann Sinna he married), against the men of Munster at the Battle of Bellaghmoon (near Castledermot) where Cormac mac Cuilennáin, King of Munster and Bishop of Cashel, was killed.
Given the biases of the Annals of Ulster, it is understood that Cerball had been a reliable ally of his father-in-law Flann Sinna.
Cerball was succeeded by his distant cousin Augaire mac Ailella of the Uí Muiredaig sept.