The best, sad there was no sequel :(
The player is able to join several of the factions that exist in Sigil (the planescape city where the game begins) including the Dustmen, Sensates, Godsmen, Anarchists, and Chaosmen. This sometimes gives The Nameless One abilities, but its main effect is allowing subquests and exploration of Sigil.
Also, the player may recruit adventuring companions over the course of the game. While there are seven potential members, only five (or fewer) may accompany him at any point.
The gameplay is unusual because of the heavy emphasis on dialog and reading. Adding a member to the party, for example, has greater impact on what elements of the story will be discovered than on combat.
The game's interface was occasionally criticized for being ill-suited for the large number of dialog-heavy encounters the game features.
According to lead designer Chris Avellone, Planescape: Torment has numerous inspirations from a variety of books, comics, and games. Notable works among them include Archie Comics, The Chronicles of Amber, The Elementals, Final Fantasy, and Shadowrun.[5]
The game begins with the protagonist, known only as The Nameless One, waking up with total amnesia. He soon finds out that he is immortal; if he is killed, he will simply reawaken in the same body (though sometimes, without his memories).
He sets out on a quest to regain his lost memories, and discover why he is immortal. As the game progresses, he slowly remembers events from his many previous lives. He discovers much about the personalities of his previous incarnations, and the great influence they have had in the worlds and people that surround him.
After traveling through many Planescape oddities and wonders, such as a pregnant alleyway, two of the Lady of Pain's Mazes, Avernus (the first layer of Baator), and Carceri (the prison plane of thieves and liars), he finally discovers why he is immortal. His original incarnation had committed a grave evil and believed that more than one lifetime was needed to atone. So, he sought out the powerful night hag, Ravel Puzzlewell, and asked her to make him immortal. Ravel granted him immortality, but, by accident, with a flaw: sometimes a death would cause the loss of all his memories. Because of this, he was unable to atone for his crimes.
Most of the playing content is in dialog-based subplots. They explain the detailed backgrounds of the characters, the past of the Nameless One, and the oddities of the setting (Planescape).
One example of a character that has a such a "hidden" background is a floating skull nicknamed "Morte", that accompanies The Nameless One from the beginning of the game. 'The Nameless One' might discover that Morte used to be attached to the Pillar of Skulls in Avernus, in punishment for having told a lie that caused someone's death, and help him cope with that.
Another examples is Vhailor, a secret character. Vhailor was a knight that believed so firmly in punishment for misdeeds that after he died, his soul remained in his suit of armor to keep punishing crimes. The player might discover that 'The Nameless One' was once one of the criminals Vhailor persecuted, and is partially to blame for the knight's condition.
There are also many subplots that help the player understand the setting. Often, making The Nameless One or other characters believe in something will make it true (because of a "consensus reality", see recurring themes). The player might also help quite a few victims of the oddities of the planes (and learn in the process). There are people that can't find the right portal to return home, people that have lost their names, and many others.
One idea that presents itself many times during the game is consensus reality-if enough people believe in something, then it is real, and begins to exist. For example, when people ask The Nameless One his name, one of the choices of response is to lie that it is "Adahn". If the player tells enough people that this is his name, a man named Adahn will appear in a certain location, claiming to be an old friend, even though he never existed before. Another example is a recovered memory of a past event in which the Nameless One apparently debates a man out of existence. Also, the Githzerai make their home in Limbo, the plane of chaos, using collective belief to shape their cities.
Another theme that is presented prominently is the possibility (or impossibility) of changing fate; many characters in torment are fighting against their natures, or against what seems to be an inevitable fate. One example is Nordom, a member of a race that has a hive mind (the Modrons) but is developing a personality of his own.
Selfishness is also a very present theme. The Nameless One has, in previous incarnations, been so committed to understanding and escaping his condition that he has been willing to sacrifice everything and everyone on that quest. Many consequences of this can be discovered through the game
War, and particularly the Blood War, are also present. The utter futility of the blood war, that started for no given reason, and seems to be endless, is cited many times.
Torment shares, of course, many themes with its setting, Planescape.