Within the jungles south of Thamasku, an ancient city half overgrown by withered vines and stunted trees crumbles into ruin. The nomadic halflings of the surrounding tribes whisper fearful tales of Tham Nusul—the Forbidden City. They tell of serpentfolk that come in the night, silent as shadows, and steal children from their cribs. They tell of plants that seek the blood of the living, and of a devil in the cisterns below the city that ensnares its victims with illusions and turns them into mindless servants. The yuan-ti that dwell in the Forbidden City raid the local tribes for food and slaves, and sometimes they grow bold enough to waylay large war parties of halflings or thri-kreen that venture too close.