In the ruins, the party found a ring that summoned a powerful djinn known as the Maad of the Air. With the wishes it granted them, they remotely destroyed the beholder Xalco (neatly wrapping up an entire subplot) and spirited themselves to Boto Kaingee's village.
Boto isn't very forthcoming but he suggests that the Adventurer's Guild is involved in something evil. They ignore his advice to retire there in Hafer and forget about the Guild, and return home to Guffin. There, they find a city that they barely recognize. Strange guards patrol the streets, few citizens dare show their faces in public, and the taverns are full of anxiety and whispers. But someone passes them a secret note advising them to investigate the house of Adrumel, where they all pledged their service to the Guild so long ago...
There in the basement, they find the mysterious shrouded statue their spoke their oaths before, fallen to the ground and revealed to be an idol of Demogorgon. As the party takes in this discovery, Adrumel comes down the stairs. He reveals that the Guild was a front for a cult of Demogorgon all along, that Demogorgon brought about the doom that felled the Parzian empire and the artifacts the Guild had sent them out to recover were, in fact, seals that had been crafted to lock Demogorgon out of the Werld. He also informs them that the Lady Blyneth and Aidan Mome are on their way to Tar-Eng to corrupt the young High King, and asks the party to join with them. They refuse, and Adrumel reveals one more horrifying secret: that he and the other Guild leaders have been gifted with new demonic forms by Demogorgon. He transforms into a Type IV demon and attacks the party, attempting to gate in a Type III demon to assist him, but with the enchanted sword Daemonrazor they manage to slay him first.
And with that climactic battle, the curtain falls on the 1st Edition Twitter campaign. I made a Storify of the battle with Adrumel, the epilogue, and my thank-yous to everybody who participated. Let me also give a shout out to MetaFilter, which let me promote this campaign on their Projects subsite and supplied me with most of my initial batch of PCs. Truly, this has been one of the most entertaining Dungeons & Dragons games I've ever had the pleasure of participating in. The story of Guffin and the Guild may continue someday on GamersPlane, where you can find me running and playing in 5e campaigns.
Thanks for playing and reading, everybody!
Taniya and Seagretor are awarded 2,204 XP each.