Over one hundred years ago, the barbarian kingdom of Sarkoris was lost to the Abyss with the opening of the Worldwound upon the face of Golarion. In response, the Iomedaean church gathered the forces of good to fight back against the demonic incursion; this was the First Mendevian Crusade. Among other victories, the crusaders destroyed the ancient temple-city of Tsar and the great citadel-temple dedicated to the demon lord Orcus within.
With their temple in ruins, the surviving high priests of this accursed demon lord fled the city with an army of enemies on their trail—an army of heroic crusaders—led by Zelkor, a powerful archmage. The exact fate of these evil priests was then unknown, for not only did the remnants of the followers of Orcus disappear from all human reckoning, but so did the First Crusade that followed after them disappear as well. Some said that the eternal scales the loss of so many good men, and with them the fortress-city of Drezen, was a fair price to pay to rid the world of so much evil.
The evil cult, however, had not been destroyed. The surviving priests and their followers instead settled on a hill near the Estrovian Forest, a sylvan woodland near the Lake Road. There they found a vast underground complex of caverns and mazes, carving out a volcanic intrusion beneath the hill. There, the priests of Orcus found the perfect lair to continue their vile rituals. For many years, they carried on in secret, hidden from the light and from the knowledge of men.
Many years later, their underground delving completed, the evil priests erected a hideous mausoleum and a sunken graveyard atop the hill. It is believed that these graves are in fact the final resting place of the pursuing First Crusade that had been destroyed to a man. Soon after the mausoleum was erected the peaceful creatures of the wood began to disappear. Though many rangers and druids investigated these happenings, the cause of the creatures’ disappearance was not immediately determined. Some years later a powerful group of adventurers, led by Bofred, a high priest of Iomedae, investigated the evil happenings and found the sunken graveyard leading to a labyrinthine complex. Bofred and his companions found great hordes of evil creatures in the complex. Though some of his companions returned from their expedition, telling tales of fantastic treasure and ferocious monsters, Bofred was never seen again—lost in the catacombs beneath the cursed mausoleum.
For the last fifty years, ranks of adventurers have ventured to the newfound dungeon. Many fell prey to bandits and monsters in the surrounding wilderness. Rumors suggest that of those who survived to reach the mausoleum and sunken graveyard, most were slain by guardians of green stone or perished on the very first level. Those rare few who return from deeper treks speak of horrible undead and creatures that cannot be slain. All who have explored Rappan Athuk offer this one universal piece of advice: “Don’t go down the well!”