Damocles Everton, the upstart master of the Blackrazor Guild and agent of the Dark Circle tops my list. Hated by the player characters after he stole control of their guild from them, the appearance of Damocles kicked off an epic story arc that culminated with the Fall of Obsidian Bay, the hero’s home city.
Everton was one of the leaders of the Dark Circle, a sinister organization founded after Obsidian Bay disbanded and exiled the leaders of the city’s Thieves Guild. The Dark Circle was obsessed with getting their revenge by overthrowing the city’s government and establishing a new order. To that end they allied themselves with the Scarlet Brotherhood, a secretive nation of assassins and monks that was notorious for overthrowing cities and governments during the Greyhawk Wars.
Everton’s allies in the Dark Circle and the Scarlet Brotherhood replaced key members of the city’s government and guilds with su-dopplegangers (a varient doppleganger that assume the shape of others and form weapons with its hands, like a magical version of the T-1000 from Terminator 2). Everton killed Justiceseeker, the city’s curmogeony cleric of Tritheron and mentor to Kalib Ironfist, one of the player characters, trapping his soul in a magic sword.
Everton’s machinations led to the invasion of the city by the Scarlet Brotherhood’s shock troops. He died in the fighting, slain by Kalib after the adventurer found his murdered mentor, seized the soul-infused sword (now known as Justiceseeker), and hunted down the villain as the city burned. For a long time Kalib carried Everton’s skull with him, casting speak with dead periodically to taunt the man and demand additional information about the Dark Circle. That lasted until some
The consequences of that story arc drove the campaign for years, and it’s still something we reminisce about from time to time.