`From the introduction:
After discovering that their “patron” intends to use the recovered dragonshards as part of some horrible ceremony (in Round 2), the characters hurry back to Sharn. There, they seek to confront Tophran Damilek, only to find that he has disappeared. The characters follow Damilek’s trail beneath the city, but must fight their way past several of his allies and minions before they can stop the ceremony that will unleash fiery ruin upon the city.
...
"After your horrifying discovery in Xen’drik—that the dragonshards you have been gathering are intended for a fiery ceremony of destruction beneath Sharn—you rushed back to the city to confront your patron, Tophran Damilek. Perhaps unsurprisingly, Damilek has disappeared from his lush residence, but not without leaving a few telltale clues to his whereabouts. Following these clues, as well as information gathered in the city itself, you have made your way through the catacombs beneath Sharn, descending ever further beneath the City of Towers. After hours of exploration, you stand at the bottom of a deep shaft before a massive eight-foot-by-eight-foot stone door."