Isobel Quinnlee (nee mac Greimdorch) was born in Castle Fitheach to Seaghd I and his first wife Elise, the second of their three children (the eldest being Seaghd II, the youngest being Coman.) Her childhood was largely uneventful, though shortly before her wedding to then-King of The Kingdom of Tir Ira III she witnessed the murder of Coman by Seaghd II, as well as his subsequent disappearance. The effect this may have had on her mental state is unknown.
With Ira, she had two children, both of which also became monarchs of Tir - Luciel and Virion II, the latter of whom would be the final King of an independent Tir. She also had another daughter, also named Isobel, who founded House Quinnlee-Tailor and whose descendant Marial I would become the first monarch of a newly reinstated monarchy some 200 years after her death.
Following the death by misadventure of her daughter Luciel, she became Queen Regent of Tir as her son was not old enough to rule at this time. In this role, she was infamously the instigator of the Tiran theatre of the devastating Imperial Wars via her paranoia and pure bad timing due to being present when the Third Battle of Sacred Pool began, having arrived there the day before on a diplomatic meeting. The timing of this has been confirmed by multiple sources to have been pure coincidence.
She was killed by the Lord Paladin in the final days of the Imperial Wars. The Lord Paladin had been captured by the UPP and was brought before the UPP leadership and Lady Isobel, where he proceeded to attack Lady Isobel and tear her throat out with his teeth before being executed on the spot by Temple of the Hand in the Water Templars.