Castle Shadowgate is the titular castle that is encountered in Shadowgate and Shadowgate 64: Trials of the Four Towers. It is built on the Gatekeeper mountains in Kal Zathynn. It was the meeting point of the Circle of Twelve during the Age of Enlightment.
The Castle Shadowgate was the most powerful castle of Tarkus as inhabited by the Druids. Composed of over 150 rooms, few are accessible to anyone but one of The Circle of Twelve. The walls of the castle are very much alive and obey the commands of the Druids; thus secret chambers are abundant.
Shadowgate was also an extremely well fortified castle; during times of war it is the most secure place on Tarkus. During the Dark Years and the Rage Wars, Shadowgate served as the Kings' stronghold and proved to be the deciding factor in the Kings' victory.
A little over a hundred years later. Del Cottonwood used the Staff of Ages on a statue of Lord Jair. The statue came to life and sent the staff into the newly risen Warlock Lord. The staff passed through the giant Spector of the Master causing a great explosion, which destroyed the Chamber of Holding, Castle Shadowgate and the mountain underneath it. Only the Four Towers built in the plains surrounding the foot of the mountain were left standing.