10 Important Video Game Plot Points That Were Abandoned
5. Mass Effect 2 - Dark Energy
Mass Effect 2 is the continuation of Commander Shepard's crusade against the Reapers, an intergalactic race of machines hell-bent on wiping out all life in the galaxy.
During the quest to recruit former party member Tali on the planet Haestrom, a subplot regarding dark energy is established and how it has been reducing the mass of a star's interior and aging it quickly. This is why on the planet itself, the sun emits dangerous amounts of radiation that can burn through armor. Data on dark energy is then revealed to be important for the Quarians, Tali's race, yet this plot thread is never mentioned again by Mass Effect 3.
In a 2013 VGS interview with one of Mass Effect 1 and 2's lead writers, Drew Karpyshyn (via Eurogamer), he reveals that dark energy was actually considered to be the Reaper's motivation for the grand finale. He reveals that dark energy could have been affecting the space-time continuum hence why the sentient machines decided to wipe out all life in the galaxy.
It is important to note, however, that while the dark energy subplot was set up in Mass Effect 2, Karpyshyn himself admits that the idea was not 'fleshed out' and was just something in consideration.