The following is a passage taken from The History of Stonegate by Shazle, and is known to be a reliable source on such matters:
"The story of Stonegate Castle is, indeed, an interesting one. At one time the keep was occupied by the Shadowlords, during Lord British's disappearance and Blackthorn's evil rule. However, once the Avatar returned our noble monarch to his throne, eliminating the Shadowlords from Britannia, a family of cyclops made the castle their home."
Ed. Note: This was the castle in which the Vortex Cube was hidden in before its recovery by the Avatar during the Age of the False Prophet
"Not more than three decades from then the walls were abandoned. This lasted but for a short time, however, for a small colony of wingless gargoyles found refuge within the confines of the keep. Three years later they were driven out by Lord Vemelon of Jhelom , who chose to retain the castle for his own purposes For several generations ownership was passed down the Vemelon line until one day the very mountains nearby opened up"
Ed. Note: It is unknown what caused this, although it has been speculated that the first appearance of the Guardian may have caused this, though evidence tends to show that it was merely a mundane earthquake
"and the swamps engulfed the castle. Now, rumors purport that a colony of trolls have taken up residence amongst the ruins, along with an ancient wizard, but no one has ever confirmed their existence"
Ed. Note: While it has still never been confirmed, the remains of ritual sacrificing tools in the area could indicate that a wizard did indeed at one time make his abode within the ruins of Stonegate, however if such a wizard did exist, he was gone long before the Avatar and his companions arrived to retrieve the Magebane, which was among the ruins.