 Thorfin was instrumental in the replacement of Godred II Olafsson as the major power in the Hebrides by Dubgall the son of Somerled.He conducted Dubgall throughout the isles compelling many local chieftains to acknowledge his authority and render hostages (1154–1155).It has been claimed that Thorfin was acting out a blood feud as Godred had played a part in instigating Óttar's murder; Godred is recorded in some sources as ruling Dublin for a short period after Óttar's death.