Dragons of Ethior
This ancient fortress was constructed over the site of an ancient foul ritual. For over a thousand years, the keep was populated with paladins, wizards, and others who were devoted to keeping the world safe from what lay below.
But one day, the dark magics kept below seeped into the dreams of Sir Keegan, the lead paladin at the keep. He went mad, slew his wife and children, and defeated hordes of his allies. Eventually, they were left with no choice but to barricade him inside the keep, locking the doors from the outside.
After that terrible event, they moved their vigilant watch to the nearby town of Winterhaven. After several generations of peace, the order slowly broke up, and many forgot why the keep was even built as it faded into the stuff of legend.