Using terms like Deus ex machina really says a lot about how little you guys took from the dialogs with the Reapers and the Prothean VI. True, they did not spell out every little detail. I grant you that, but it does not take much imagination to consider what happened? And why it happened?
RealStyli, I appreciate your reply, and it definitely helps me realize there are some normal people in this crowd. I can explain my interpretation of the ending, and what it means for the future of this franchise. I am not saying it is definitely what happened, it's just where my mind filled in the blanks. The reason I would have avoided this under normal circumstances, is that it is incredibly nerdy to go this in depth for an argument about a sci-fi story. But, oh well. For me, it's not so much how it ended, as it is the fiction itself.
The thing I think most people conveniently forget is that a human being lives in a time scale of around 100 years. A Reaper lives in time scales of beyond 50000 years. For whatever reason the Reapers snuff out all advanced life at 50000 years, you can rest assured that it is for a reason on a scale that dwarfs the concerns of life or death of one generation, no matter how many.
Ok, so, that sucks for people alive right now. They find out they are extremely late to a party that the Reapers have already started, millions of years before their planet was even born. Alright fine, their purpose is ancient. Beyond ancient.
But then what is reason for their purpose? This is something BioWare did not spell out directly, and most science fiction will leave vague anyways due to it being VERY hard to explain what, on a scientific level, could have such vast implications. However, there are a few events in the universe that do have such far reaching implications, at least in theoretical science. This is where my head filled in some of the blanks:
The Reaper on Rannoch says: "You represent chaos, we represent order. Every organic civilization must be harvested in order to bring order to the chaos. It is inevitable. Without our intervention, organics are doomed. We are your salvation."
Chaos, can also be explained as Entropy. (
http://en.wikipedia.org/wiki/Entropy)
"The second law of thermodynamics states that in general the total
entropy of any system will not decrease other than by increasing the
entropy of some other system. Hence, in a system isolated from its
environment, the entropy of that system will tend not to decrease. It
follows that heat will not flow from a colder body to a hotter body
without the application of work (the imposition of order) to the colder
body. Secondly, it is impossible for any device operating on a cycle to
produce net work from a single temperature reservoir; the production of
net work requires flow of heat from a hotter reservoir to a colder
reservoir. As a result, there is no possibility of a perpetual motion system. It follows that a reduction in the increase of entropy in a specified process, such as a chemical reaction, means that it is energetically more efficient."
In other words, energy can not be created or destroyed. It can only be converted, or manipulated. The natural flow of energy (or heat\\motion)
in a closed system without influence, is for energy to disperse. Order, in any form, is the most difficult state particles can assume. This is why perpetual motion is impossible, because this is a law of nature.
With that in mind, what does that have to do with Reapers, and their intent?
Heat Death... (
http://en.wikipedia....of_the_universe)
"The heat death of the universe is a suggested ultimate fate of the universe, in which the universe has diminished to a state of no thermodynamic free energy and therefore can no longer sustain motion or life. Heat death does not imply any particular absolute temperature; it only requires that temperature differences or other process may no longer be exploited to perform work. In the language of physics, this is when the universe reaches the maximum entropy."
"The idea of heat death stems from the second law of thermodynamics, which states that entropy tends to increase in an isolated system. If the universe lasts for a sufficient time, it will asymptotically approach a state where all energy is evenly distributed. In other words, in nature there is a tendency to the dissipation (energy loss) of mechanical energy (motion); hence, by extrapolation, there exists the view that the mechanical movement of the universe will run down, as work is converted to heat, in time due to the second law."This is a real theoretical possibility for the "end" of the universe. Where by, all interactions, of any kind, will cease to be possible. In terms of Mass Effect, that Reaper on Rannoch says that all life must be "Harvested". The only reason I can see this as being necessary, is if life, as we know it, causes entropy to increase in the universe, faster than it would naturally. But since energy can not be created or distroyed, this could be the way for the Reapers to continue a cycle of life, without causing irreversible harm to the universe. It seems particularly devilish to have to wipe out whole species, but when you take in to account things like the Krogan, who multiply faster than the galaxy can even support, or evolution where organics are actually creating new life forms (the Geth, etc). The cycle leads toward an energy usage singularity. At a certain point, there would be no way to return order to the entropy, and the possibility of heat death of the universe would take place.
A particularly advanced race in the early galaxy\\universe could have seen this as the ultimate problem facing the cosmos. They created the Mass Relays, the Citadel, and the Reapers, in order to allow life to continue, as a renewable resource in regards to the universal amount of total energy available.
I also think that the Crucible could have been created by the same people who made the Mass Relays, Citadel, and the Reapers, as an end game for the cycle. That's where Shepard and his choices come in to play. You have to think of the game more like Heavy Rain, and less like Chrono Trigger at this point. There is an end, and the story will get there no matter what you do. The end goal is, getting the crucible built and using it. Your choice at the end, has to be made, though. The cycle has to end, one way or another. Option 1: The Reapers can do their thing, and take the entire galaxy, like they have always done. Option 2: Use the crucible.
If the Crucible was designed by the same people who made the Reapers (etc) then it makes sense that they still call the shots. The crucible ends the cycle by removing the reaper harvesting forever, but the stipulation is that you can no longer evolve on the paths they have chosen. For better or worse. I'm not sure what that means in regards to chaos and order, but perhapos the Synthesis ending is the correct answer?
TL;DR: Just one fans thoughts.