After Winter Diamol pressed upon you some artifacts from Vesh Toraein's vaults, you gathered around the newly open basement door to investigate. Aleksander O’Laighin stepped through the door and vanished, and the rest of you soon followed.
You found yourselves in a vast underground space, utterly dark. You stood upon a stony plain, virtually featureless except for a door-sized stone arch through which you had just passed. Stepping back through the arch did not take you back to the Rose Tower, so you determined to explore your new surroundings. Wil was able to discern what seemed like a faint trail across the plain, and you followed it.
Your new environment reminded Lord Desideratus Constantin Lycurgus Xenophon, Ehrkun of Gorizda, Sixth of His Name (aka Betty) very much of his time in the Underdark, the underworld where Mistress Lolth consumes the souls of those not chosen by the Raven Queen to live in paradise. Your journey across the plain sparked memories in him of running across just such a plain, pursued by some terrible monster. It also seemed to inspire unusually lifelike feelings in Almos, Desideratus' zombie manservant.
By the end of the first day you had ventured through the darkness into a sort of underground foothills region. That night you were visited by an undead creature of shadow that appeared to Wil as an eight year old boy. The boy claimed to be Wil's long-dead infant son – a suspicious claim, as Wil's son died an infant fifteen years ago. Convinced that the creature was not the soul of her child, Wil attacked it. The child retaliated, aided by Almos, but was driven away after a sharp fight. It fled in pain, crying that you didn't love it.
The next day, still following the trail from the stone arch on the plain, you came to an area of the foothills riven by fissures: some mere gullies, others yawning chasms. You also encountered a stone bridge, clearly artificially constructed and carefully repaired more than once. The child creature warned you as you approached it that on the other side of that bridge lived mean and angry people who made bad music.
As you crossed, however, you were attacked not by people but by swarms of poisonous spiders and a single giant spider. The child also attacked Aleksander, psychically wounding him and then exclaiming in frustration that he was not happy either. Aleksander retaliated with the divine power of Pelor, revealing many faces within the shadow child, and driving it away once again.
You fought your way through the initial wave of spiders, but as more poured from the chasms and stalagtites around you, you were forced to run. When you had at last outrun the swarms, you saw torches riding towards you in the distance. The newcomers were orcs riding giant boars. You attempted to communicate with them, but none of them spoke your languages and none of you spoke theirs. They reacted with alarm when Desideratus attempted speaking to them in Draconic, but did not attack. In the end, they beckoned you to follow them, and you set off in their company across the underground badlands.