A dracolich and his sorcerous queen have seized control of the Mythal, the ancient magic that once protected the long abandoned elven city of Myth Drannor. Once the elven ruin is completely in their thrall, the cult intends to expand its domination one city - and one soul - at a time.
Four heroes are sent to Myth Drannor by Elminster to stop the dracolich and the sorcerer queen from using the power of the Mythal to conquer Faerûn. They must travel to all areas of Myth Drannor, from the dungeons below the city, to the city itself, the catacombs beneath the city, et al., in an attempt to stop the evil from taking over the region.
Source: Wikipedia, "Pool of Radiance: Ruins of Myth Drannor," available under the CC-BY-SA License.