The party couldn't do anything without first dealing with Oonagh's missing soul. Meeting with the Ghaele of Winter herself with a souless Feylock could be seen as an insult, so the party opted instead to wander the market seeking information.
Kali ran into Lucius, the Tiefling working for the Order of the Chain, sitting at a stall enjoying a cigar and an espresso; his Ogre bodyguards, while less refined, were happy to be at the market as well. Lucius wished her a good day and thanked her and the rest of the party for helping the Order of the Chain to take over Brightmoon: He'd hired the Thieves' Guild to force them to rob the town, and the Order, and this had been excuse enough that the Order arrived with a legion of Ogres and conquered the place. The Tiefling also informed her of Lanu's powers: she had the power to reveal that the Thieves' Guild were all Lycanthropes, Werewolves and Wererats, and caused them to fight one another. He offered to "take her under (his) wing" and give her a fine education and life with the Order; Kali refused.
Overhearing all this was the Dragonborn, Bahamus. He was no friend of Lucius, and listened in on their conversation. He watched Kali leave, and watched the arrival of Lucius' twin sister Malicia; equally gorgeous, but sensual where her brother was smooth, with an obvious taste for blood where her twin's taste was for… this finer things in life.
The dragonborn then tried to follow Kali. Bahamus was less quiet than he'd thought to be, and Kali confronted him. The two of them expressed equal hatred for Lucius, and when the rest of the party arrived, Bahamus joined them (as they'd rescued him from the dungeon where Lucius had tricked him).
The party met with the Artificer Trull in his workshop, and discovered he'd been led to them by a strange dream. A device in his workshop, powered by a sliver of Rainbow he'd found, could be used to make a portal to another world. Oonagh's soul was on the other side, and he was to help the party get to it and get back.
The party then slept, and each of them had the same dream: the party was flying over a pale white landscape on dragons and magical horses. Lanu was with them. The land was on a world, and their homeword was in the sky above them, like the moon. Also in the sky was this land's own purple moon. The purple sphere was somehow filled with evil, with malice, and pulled Oonagh (who was like a corpse) up and away from them. It then turned to the rest of the party with a horrific scream, waking them from the dream with psychic pain.
The party went through the portal, and arrived on a strange purple desert world. The wind was fierce, blowing grit into their faces, and on the wind was a horrific scream like the one from their dream. Around each of them was a glowing white nimbus of light, which they realized was their mental sanity; as long as they were on the planet it would slowly decay. They looked up a rise and saw a massive black pyramid; Oonagh's gaze looked up to its tip, and they knew her soul was in there.
Entering the pyramid, the party found it guarded by a race of black-furred beastmen whose bodies were covered in tiny mouths and alien eyes. They fought with claws and hunters' bows, and attacked the party with the pyramid's traps. Room after room, the party fought their way through until they reached the top. There they confronted more of the beastmen, and a horrific creature: the beast from the dream! The creature floated up out of a well in the floor and struck at them with sanity-destroying screams, hitting Xtapa and Bahamus most of all.
Xtapa surged forward, unleashing his primal fury, to slay the beastment. Oonagh however began to wander towards the creature, and climbed up on the well as if to jump in. The barbarian grabbed her, dragged her over to a room off the side, where they found dozens of glowing crystals filled with souls (like some sort of collection of magical jars). Three of them claimed to be Oonagh, but only one of them knew who Lanu was. Grabbing the crystal, he touched it to her and bam Oonagh had her soul back. She quickly grabbed her bag of holding (purchased in the Market) and filled it with Soul Gems of other souls also trapped in that room.
Kali faced the creature with many radient lances of faith, but when Oonagh's soul was returned the party decided to flee before their sanity was further eroded. They dashed madly through the Pyramid, followed by theechoeing laughter of the creature, out through the desert to leap through the portal.
The party then took an extended rest, glad to be back. Lanu hugged Oonagh, and the party was well.