Kalends of January
. AD 821.
Mac Riaguil grandson of Magléne, scribe, bishop and abbot of Biror, died.
Abnormal ice; the seas, lakes and rivers froze and herds of horses and cattle, and loads, were brought across them.
Murchad son of Mael Dúin made an expedition with the men of the North to Ard Brecáin. The men of Brega, i.e. Diarmait son of Niall and the descendants of Aed Sláine, then went over secretly to Murchad and submitted to him at Druim Fergusa. Conchobor son of Donnchad invaded Brega and camped at Gualu. He invaded southern Brega again on the Kalends 1st of November, and a vast number of the men of southern Brega fell by him, and the Uí Chernaig submitted under compulsion.
Death of Forbasach abbot of Achad Bó Cainnig.
Cumuscach son of Tuathal, king of Ard Ciannachta, was killed by Murchad.
The battle of Tarbga between the Connachta themselves. The Uí Briúin were overthrown and very many nobles were slain, including the leaders, Dúnchad son of Maenach, and Gormgal son of Dúnchad. The Uí Maini and Diarmait son of Tomaltach were victors.
A slaughter of the men of Bréifne, including their king, i.e. Mael Dúin son of Échtgal, was inflicted by the Cenél Feidilmthe.
The men of Ard Cianacht, were routed by Cumuscach son of Congalach, and Eudus son of Tigernach and many others fell.
Eochu grandson of Tuathal, anchorite, bishop and abbot of Lugbad, fell asleep.
The Uí Garbáin, the Cuircne, and the Felle routed the Delbna.