Numenera was originally a setting created by Monte Cook, famous for begin a one of foundubg game designer for the Third Edition of D&D (He's probably even more infamous for having really OP spellcasters).

The Premise of Torment: Tides of Numenera So of course someone would try to do a follow-up. P:T was not a financial success, but the game's charm and writing made it a instant cult classic. All of this under the shadow of the question 'What can change the nature of a man?'. You would have some very lenghty and wacky conversations with various characters and getting into strange situations. You played as an amnesiac tall blue-ish guy barbarian-looking (but not a barbarian) wearing a loincloth and dreads, instead of going in a grand adventure to defeat an ancient evil, you went in a journey of self-discovery. Planescape tried to do something original on the TTRPG/D&D world and Planescape: Torment also tried to do something different for the videogame RPG world.

Borrowing from the most popular RPG of the 90s, Vampire: the Masquerade, the city was divided between factions with very dinstinct philosphies, 'good and evil' were way less distinct and the game also had a more 'reflective' tone.

Planescape was an attempt to renovate the decadent AD&D by breaking from more tradition D&D settings, instead of the generic medieval fantasy it was set in a closed city in the middle of the multiverse which had portals lorlinking to other planes and the heavens and hells. It was set in the 'Planescape' campaign setting for Dungeons & Dragons. 'Torment', or rather Planescape: Torment was initially a cRPG released in 1999.

Torment tides of numenera necropolis