Balor is likely a country or kingdom in Albion, roughly a day's ride from Camelot. It is located nearby to the Mountains of Isgaard. Conjecture of its existence was based on the names of a wooded area – the Forest of Balor – and an underground cavern – the Caves of Balor – that occupy the same tract of land.
Arthur Pendragon once traveled to the forests and caves of Balor in search of the Mortaeus flower, where he was challenged by Nimueh. (The Poisoned Chalice).