The pass is located at 1500W 1442S, in the lower portion of the Stonewall Range. The general location is mentioned by rumors in Caladon, and its purpose as a quest location is hinted at in the book The Pagan Gods of Arcanum written by Aldous T. Buxington III of Tarant. It is marked on your map by exploring the immediate area, and it can be used as a way-point after successfully tranversing it at least once.
Gorgoth Pass is well guarded by a variety of beasts, golems, and elementals -- so be prepared for a long and dragged out running battle. Conversely, speed or invisibility can be used to get through the pass without a fight.
At point 1 you can find (hexed) consuming plate mail on a lootable corpse.
At point 2 you can find Kaitan's altar, which is part of the Ancient Gods quest. Kaitan wants a geode. Conveniently, you should find a geode on the ground nearby.