According to Heart's End; the World Below, also known as Manifold 11, is ruled by the Queen of Night, an ancient Celestial, and sister of the Queen of Winter and the Queen of Shadows.
The World Below, is inhabited by the Astral Celestials and their creations, the dark elves, or drow, who were banished there from the Munane world. The Star Elves also brought with them humans from the mundane world, and they are now known as the Hlan or the deep men. Other inhabitants include Quaggoths, Kua Toa, Duergar and Mindflayers, the Voiceless talkers. It is the main place where Sin Metal and Starmetal (rovion), can be found, as it was made by the Star Elves.
- Zanzerite, City of the Glass Pool, a ruined drow city inhabited by Svifniblin.
- Xanazaar, City of the Speaking Stones, ruled by the drow House U'laas.
- Orr Mal'azar, City of the Black Star, the largest city in the world below, ruled by the drow House Osstuyl.
- Avarak Sul, a Duergar fortress.
- The Palace of Varnal
- The Sunless Sea
- The Isle of the Dead
- The Isle of Madness
- This was revealed during Ep 15 of Dusk https://www.twitch.tv/videos/1233073235?t=00h53m36s
- Kingdoms and Warfare pp. 217-9