Skein of the Abyss
The Skein of the Abyss is a howling pocket dimension where travelers occaisionally become trapped when a dimensional journey goes awry. Virtually all of the Skein is a ring. The traveller is doomed to return again and again to the obelisk where they gained entry. In time, the lucky may solve the mystery of the obelisk's functions. Beware the watching. They are implacable, though not hostile to everyone who passes.
The Skein overlooks a portion of the Greater Abyss. If the trapped traveler is unable to find an exit, in time the temptation to jump into that Abyss and escape the eternal howling may become unbearable.