Complex sentence: The main beneficiary of this was the Cenél nEógain, whose gains came largely at the expense of the over-kingdom of Airgialla in central Ulster, whose centre was pushed into southern Ulster as a result.
Split into simpler sentences: The main beneficiary of this was the Cenél nEógain, whose gains came largely at the expense of the over-kingdom of Airgialla in central Ulster. Airgialla's centre of power was pushed into southern Ulster as a result.