He was the son of Máel Cáich mac Scannail (died 666), a previous king.
In the 6th and 7th centuries the Dal nAraide were part of a confederation of Cruthin tribes in Ulaid and were the dominant members.
In 682 Cathassach fought with Britons at the Battle of Ráith Mór, east of Antrim, capital of the kingdom.
Cathassach was slain as was another Cruthin king, Ultán son of Dícuill of the Latharna, modern County Antrim).
This biography of a member of an Irish royal house is a stub.