The clan predates human habitation of Wyvern Hill. In 995 CE, the gargoyle who would be known as Demona and the Captain of the Guard betrayed the clan was to Hakon and his Viking marauders. Hakon and his men attacked the castle during the day, when the gargoyles slept, and with the help of the Captain of the Guard, managed to overtake the castle's defenses. Hakon, in a fit of paranoia, had his men destroy all the sleeping gargoyles. When Goliath and his mentor returned to find that all but a trio of gargoyles and a single gargoyle beast had been destroyed as they slept, they sought out the Vikings for revenge of their clan's annihilation.
The Magus of the castle, thinking his beloved Princess Katharine was dead at the fault of the gargoyles, cursed them to sleep "until the castle rose above the clouds." This spelled out the end of the Wyvern clan, with the survivors trapped in sleep, and the eggs yet unhatched. The sleeping survivors went on to form the Manhattan Clan, and the eggs, taken by Princess Katharine, the Magus, and Tom, were taken to the magical island of Avalon, where they hatched and formed the Avalon Clan.