Throughout Fallout 3, the Lone Wanderer will make decisions and be given choices that will change the face of the Capital Wasteland. While many of the quests and options will be more morally gray, some have clear good or evil outcomes; that's where Karma comes into play. However, as the system has been absent from the franchise since Fallout 4, newcomers diving into Fallout 3 for the first time might be left scratching their heads the first time Karma is mentioned on screen.

Karma was first introduced to the Fallout game series in Fallout 2 and replaced the reputation system present in the first Fallout game. After that, the system was expanded on and included in Fallout 3 and Fallout: New Vegas, the latter of which also had a reputation system working alongside Karma. When playing the older entries of the series, understanding how Karma works and what it will affect is essential, especially when planning for certain playthroughs.