As I am replaying the original trilogy, I have been thinking about who could be the next big antagonist for the new Mass Effect game (if we ever get one).
So, the Reapers are gone, and they set the bar pretty high. For a billion years, they have purged advanced species of the Milky Way. Mighty empires crumbled before them and were wiped out, leaving only crumbs to pick up for those that came after them. Or is that really the case?
What could be more terrifying than the Reapers? A species that survived despite them. A billion years is a long time. What if an alien race adapted itself to the cycles? Let's say a primitive version of that race encountered a prior Reaper invasion (similar to the Reapers that visited Stone Age humans) and maybe even witnessed the destruction of their predecessors. Although they were primitive enough to escape the harvest, they were able to understand the Reapers for what they were — an evil deity that punished advanced civilizations. Civilizations that were too prideful.
As a consequence, their culture became dominated by the fear of the Reapers. Technological advancement was not prohibited, but shaped by the need to stay hidden. This species, for example, would never broadcast electromagnetic signals into space as we do. And somehow — they managed to survive their scouring.
How they did it is unknown.
1) Either they were able to migrate away from their planet, far from the mass relays, escaping the watchful eyes of the Reapers. From there, they would observe and study the destruction of the Milky Way galaxy.
2)Another theory suggests that, making use of an elaborate scout system, they could scan the universe for signs of an incoming Reaper invasion. If these signs were detected, the entire species would fall back into a primitive state.
Cycle after cycle (experts suggest they survived 6-8 cycles), they became better at hiding from the Reapers. However, one thing never changed: they knew that under no circumstances should the gods be interfered with.
But in the last cycle, something changed. Scout systems all over the Milky Way reported that the Reapers were defeated. How is this ancient species, which was kept in check for so long by the apex predator, supposed to deal with this new reality?