Upon discovering their epic destinies, the Fancy Bastards find themselves under the Seven Shields Coalition’s protection in Sayre where they meet an angel of secrets who calls herself Rachaela. Rachaela tells them the tale of Mornujhar and impresses upon them the importance of finding out what his ritualist is up to and stopping it. Rachaela pays the adventurers to travel to Monadhan, use the portal leading to the shadowed demiplane of Vaerothim, and confront the ritualist once and for all.
The heroes’ trip to Monadhan is complicated by the difficulty of willingly leaving Monadhan, a supernatural prison for traitors and betrayers. To use the portal, the heroes must find Monadhan’s key: whatever object in the realm is the most potent symbol of betrayal. They must also defeat Arantor, the dark lord of Monadhan—an undead dragon which guards the portal itself.
Once in Monadhan, the Fancy Bastards travel through the jungle and reach the shantytown where most of Monadhan’s denizens—a sorry mix of betrayers from all realms and times—live their lives in squalor. They speak to a seer named Sarissa, who reveals that the current key to Monadhan is the Sword of Kas, the artifact that cut off the hand of the god Vecna. Their inquiries put them into conflict with vampires skulking around the shantytown. After several battles,
the heroes learn that the vampires are working for Kas himself.
Kas confronts the Fancy Bastards and offers them a bargain: he will tell them how to defeat the dark lord that guards the portal if they recover the Sword of Kas and turn it over to him. The Bastards realize that Kas doesn’t know that the sword is also the ticket out of the domain of Monadhan. Kas keeps his part of the bargain and tells the adventurers how Arantor’s grief and shame over his own horrible crime — the slaughter of a village and the murder of his daughter centuries ago — takes tangible form in the lower cavern of Arantor’s lair. Making Arantor’s victims come to life may distract and weaken the dark lord enough that the Bastards can win the day, recover the sword, and use the portal.
After fighting their way through magical caverns that rearrange themselves, the heroes reach a final showdown with Arantor. Using their tactical acumen, the power they’ve acquired thus far, and Kas’s advice, they defeated the dark lord. Then they decided to betray Kas and keep the sword for themselves so they could use the portal to reach the demiplane of Vaerothim.