Chaulssin is a drow city in the Underdark. To some people it is also known as the City of Wyrmshadows. Chaulssin lies beneath the northern Rauvin Mountains. It overhangs an extremely deep abyss and cold winds howl permanently through the city. It rests upon a great spar of stone. After it was conquered by shadow dragons and ruled by their descendants the city was partially brought into the Plane of Shadow. Tendrils of shadow-stuff wind all the time through the city and deadly shadow creatures haunt the streets. Sometimes whole quarters of the city vanish into the Plane of Shadow and reappear years later.