Highcastle is a frontier town and a barony located on the western side of the Teeth of the World. It is the largest one of the three Border Baronies of the Kingdom. The other two were Northwarden and Ironpass.
During the Great Uprising, Prince Arutha, Guy du Bas-Tyra and his group escaped to Highcastle after blowing up Armengar. They were received by Baron Brian Highcastle, who did not believe their word about the army of moredhel and goblins.
They were able to escape the fortress as it was overrun by Murmandamus' army, killing the baron himself.
Since then, the fortifications there was reinforced to discourage further incursions into the Kingdom of the Isles.