They head down to Mez, launching at the port village of Mochly and leaving Ben there with the wagon and horses. They sail down without incident, meeting a boat full of halfling heroes on their way to wipe out the gnome cult that has taken hold in the Barrowlands.
Upon arrival near the hills surrounding the mastaba, they hear sounds of combat and find an elf fighting a manticore. They help him and learn that he is Kylwin the Bold, a Guild scout down here investigating the Xalco situation. He joins the party.
Afterwards, the party meets a shedu named Sulpa-Uddu who warns them to stay out of the Valley of the Wise and not disturb the Yellow Disc. They disregard his advice and proceed down to the valley, where they find a copper dragon napping on top of the Mastaba of Aptor. The dragon wakes, and while the party tries to talk him into letting them pass, he explains that he has been given license to eat any who intrude in the valley. The party tries to subdue him at first, his strength is such that they quickly change to an all-out battle and slay the dragon.
Inside the mastaba, the party encounters a few traps, including a mimic chest and a stone head that shoots magic missiles, and they loot some gold and jewels, some of Aptor's childhood toys, and three cursed pieces of jewelry. But the sarcophagus has been smashed in, and a strange tunnel has been bored into it, miles long with faint octagonal patterns in the dirt. The party hikes to the end of the tunnel, coming out on a hillside on the other end of the valley. There they are confronted by two couatl, Yopat and Chac, and Sulpa-Uddu. The party explains that the Disc is missing, and they suspect a trio of lamias who were seen on this hillside a few days ago. As the guardians of the valley cannot act outside their jurisidiction, they ask the party to venture to the Murmuring Cave where the lamias make their lair and retrieve the Disc. The party agrees to turn the Disc over to them instead of the Guild, and Yopat removes their cursed items. They are flown near the cave.
Inside, the party encounters the three lamias, Abit, Illan, and Tamar, resting near an underground pool. Abit holds the Yellow Disc. They see Hinonk first when he accidentally makes some noise laying caltrops for an ambush, and ask if he is the messenger they've been waiting for. He tries to bluff them, but fails, and Illan casts a Charm Person spell on him. Tamar looses an earth elemental (who they've nicknamed Dirt) from an iron flask, controlled by a magic stone, and the rest of the party reveals themselves. Illan entices Hinonk to stand next to her, effectively taking him hostage. Stuck in a standoff, the party and the lamias talk for a bit, and when Hinonk reveals that the party is from the Adventurer's Guild in Guffin, the lamias are taken by surprise, as the messenger they are waiting for was sent by one Aidan Mome from the Guild.
Eventually, the lamias' quasit familiar, Pheltch, returns with news that the messenger will be arriving soon. While waiting for him, Hinonk and Tamar play a board game with a set they looted from Aptor's grave goods.
The messenger arrives via flying carpet, and it turns out to be none other than Adrumel, the Sword & Rod, third highest ranking member of the Guild. He takes the Disc, explains to the party that a contingency plan to recover it has been made, and that he's impressed they managed to track it all the way here. He escorts them out of the cave and leaves.
The party returns to Sulpa-Uddu to explain what happened. He is horrified by the loss of the Disc, believing that if the wards on it are broken, something terrible will happen, having previously alluded to some doom that befell Parz, was avoided by Mez, but might now be repeated in Engol, which seems to be related to the Disc in some way. He leaves to confer with the couatl brothers.
The party hikes back to their ship and finds it gone. They pay a passing trader to take them back to Mochly.
Mysterious gifts are given: a bundle of wolfsbane for Gnaurm, a spyglass for Eryn, a book (A History of the Land and Peoples of the Suprora Forest, by Aelgeth Thrifelwine) for Taniya, a silk dress for Baella (Taniya's NPC partner), a felt pouch for Cymerick's oracular knucklebones, a leather pipeweed pouch with an embroidered rabbit for Hinonk, a fighting net for Grabathor.
Taniya pays ben 5 GP to wait at Mochly, drinks her potion of healing,
Hinonk claims Drimmo's short sword +1.
The party loots amethyst-and-jade grapes and golden stalks of wheat worth 5,500 GP.
The party pays 100 GP worth of the golden wheat for passage back home and loses its ship, the Mermaid.
Each party member receives 1,767 XP.
Hinonk is awarded 1,000 XP for excellent roleplaying while under the effects of Illan's Charm spell.