Castle Krab'Maga

Castle Krab'Maga is the ancient castle of the first Hobgoblin King, a mythical figure whose name has been lost to history. The Hobgoblin King united the warring goblinoid warbands and bent the warlords to his will. Uniting all of goblinkind into a single unified purpose. It took the combined forces of Kotland, Zirdy, and the Wildlands to hold them off long enough for the king to die. Since that time the castle has been occupied several times by would be kings. Strict tradition stops any warband from claiming the castle without the several other warbands recognizing the king.
It is made out of an unknown stone that has stood the test of time. Siege weapons don't seem to effect it. The gate has been replaced countless times but the walls have never fallen. Similarly extensions have been built on using mined materials but these have always fallen over time, leaving only the dark grey original original structure.