You gain access to Goblin Castle by first navigating your way through The Labyrinth. If you need help finding your way in The Labyrinth, you can find a link to a map on the Map Page. The main mob in this zone is the Goblin King. You can sometimes find a Crimson Iron Ring of Regeration on him or a Staff. Great zone for low level Characters. Clerics can solo this zone soon after they get Sanctuary. Good Luck.