The Dark City also known as the city of Korimar. Built one thousand years ago by a cabal of mages called the Order of the Veil. They wished to create a planer metropolis on par with cities such as Union or Sigil. They did succeed but since then the order has vanished from the city.
Said to be nearly impossible to reach by all but who have been to the city or receive instructions on how to get there. The Dark City remains a great mystery to most of the outside world.
The letter you received.
To whom it may concern,
Gailen Brell.
The letter contains directions to reach the city.