A regular day turned positively sour as a gigantic purple worm burst forth from the ground, shattering the walls of Regus in an absolute mess of an attack.
Drow raiders quickly burst forward, ransacking the city while the worm thrashed about. The city itself was absolutely lost, the last few survivors hurried away in a portal by the adventurer's guild.
The remains of the city were picked apart by raiders, scavengers, and whoever happened to be passing by. Whatever remained of the once-great city laid in ruins, though it gave way to the perfect citadel for the Devil lord Perilor. Adventurers had brought the Devil lord to the city, he laid waste to the worm and took over the city. It became populated by the Brimstone Cultists, an organization based on gathering the world's magical artefacts.
In time, Perilor discarded the ruin of the city and his fortress for more magical pastures. Before vacating he instructed his cultist followers to dismantle his fortress, leaving the ruins nothing but a mess of stone.
Recently the half-elves in exile have decided to take back their ancestral home and rebuild the once great Regus.
