Complex sentence: The head of Sliocht Eoghan of Coshmaing was styled as Lord (Ard Tiarna) of Coshmaing (English: "Cosmaigne"), with the principal seat at Molahiffe, as well as castles (sub-lordships) at Fieries and Clonmeallane.
Split into simpler sentences: The head of Sliocht Eoghan of Coshmaing was styled as Lord (Ard Tiarna) of Coshmaing (English: "Cosmaigne"). The principal seat of the Coshmaing lordship was at Molahiffe, with other castles (sub-lordships) at Fieries and Clonmeallane.