Penumbra: Requiem is an expansion to Penumbra: Black Plague meant to tie up the loose ends of the game. It is the third and final game in the series and requires Black Plague to play.
Unlike the previous two games, there is no full storyline, no enemies and no real action sequences. The player's flash light also has an unlimited amount of batteries. Instead, it brings closure to the story regarding the fate of Philip, the protagonist of the series, through nine areas based on locations from the previous games and solely based on solving puzzles. Each location is connected to the other one through a portal and there is nothing else linking them in a logical sequence. The puzzles are all physics based and require the player to examine the environment, manipulate it and usually find a way to power the portal to move on to the next area. Often, the player will need to buy structures with elements from the surroundings to reach other areas.
Story elements are provided through narrated sequences through diaries discovered in the areas. Each of the nine locations also contains a hidden artifact. When all nine of them are collected, the ending is expanded with additional pieces of information.