From Black Isle Studios: "Welcome to Sigil, the City of Doors, a place with gates that lead anywhere in existence provided you have the proper key. It is a neutral ground and watering hole for... More > races across the multiverse, all under the watchful shadow of the Lady of Pain, the enigmatic ruler of the city. It is a place where the word is mightier than the sword, where thought defines reality, and where belief has the power to reshape worlds and change the laws of physics."
http://www.wischik.com/lu/senses/pst-book.html --> "Original text by Chris Avellone and Colin McComb. Novelization by Rhyss Hess. Planescape: Torment is an emotionally deep, thoughtful computer game. You play an amnesiac immortal in search of his past and future. Rhyss Hess played through the game, wrote down all the dialog, and added enough narrative to make it flow like a novel."< Less