The Catalyst is in the Citadel it is not THE Cidtadel

Were the parameters of the Catalyst to commit genocide against its creators?  I actually engaged in the behavior it was supposed to stop.  Sounds to me like it had very little in the way of restraint.  If my phone were super intelligent and had no constraints, it might well begin to do things that are harmful to us.  Think of the AI on the Citadel from ME1.  It couldn't do much in the form it had.  But it was smart.  It funneled money so that it could be taken to geth space and possibly turned into one of them.  If Shepard doesn't discover it, presumably it succeeds.  My super intelligent phone might be able to do the same, granting it mobility without constraint.  It was made for certain functions but, for example, Google Duplex is able to make reservations on your behalf.  Once you start giving it the ability to do things on your behalf, you run the risk of it doing things you don't want.

Now take this to a super intelligent AI that can create pawns to use against others.  Even if it couldn't turn on its creators (the Catalyst was able to do that), the pawns could.  They could be created to do whatever the super AI wants, including building a base over which it has complete control.  Not doing so it as bad a flaw as the Leviathan made in creating the Catalyst in the first place.

Yeah, it's not the first time we've had to deal with that type of no-win-scenario either, such as in "The Arrival" for ME2 when we had to sacrifice the entire Bahak system so the Reapers couldn't use the Alpha Relay.

I prefer the EC ending of Destroy because it seems to imply that only Reaper technology was affected/destroyed, rather than it triggering a technological apocalypse everywhere. Even if all tech in the Milky Way does derive from Reaper tech according to ME1, it's so distantly removed and low-tech in comparison, it might not even be affected at all?

The real tragedy from this is that the Geth may have unwittingly doomed themselves by upgrading with Reaper tech, as that might have been what made them susceptible to the effects of the energy wave triggering the Reaper shutdown/destroy command. EDI on the other hand was always doomed, as Cerberus built her using Reaper tech.

A quote from Age of Ultron that seems very applicable to the Catalyst;

I agree, Destroy was the only way to wipe the slate clean and destroy the Reapers for good. Sure it may come with a cost of Shepard bringing about the (unwilling) genocide of all current Synthetic life, but the other two endings would have Shepard let the Reapers off the hook for billions of years of galactic genocide.

I don't see how some people can think Destroy is out-of-character or a renegade choice for Shepard to make, when defeating the Reapers and breaking the Cycle has been Shepard's goal ever since the first game? In all three games, Shepard never sought to control the Reapers like the Illusive Man or attempt to merge with them like Saren did. At most they may have chosen to co-opt the Collector base to gain a technological advantage to better even the playing field, but that's about it.

Catalyst probably controls the area directly around it. How ever the entire base story of the Citadel is that no race ever explored it fully. Hence why no race realized it was a mass relay. The mechanisms to activate into a mass relay powerful enough to reach beyond the edge of the galaxy would be far larger and more connected to the over all structure then the space it would take for the Catalyst to reside in.  If they can't find that them not finding the Catalyst isn't a stretch of the imagination.

The Citadel is bait to the rest of the galaxy kept up by the specifically created Keepers. They maintain the entire station and are the ones that react to the signal to activate the Relay.  Literally all the important aspects of the Citadel are already build into the Citadel for self maintenance and secrecy.  The Reapers are shown to be capable of independent thought and action even if they are guided by a single mind they are very much like the  Rachnni. Each worker is capable of independent thought though they all obey the Queen when she says to do something.  That said the Reaper Signal the mode of communication isn't very well understood how ever it is shown to be powerful. Possibly some sort of advanced Quantum Entanglement Communication.  It took months and thousands of sacrifices for Cerberus to learn how to just barely over ride control of Husks. And the second the jamming field went down it attracted Reapers from hundreds of light years away.  The thought that the Catalyst could have an advanced and miniaturized version that would allow it to communicate across the galaxy while being contained within it's own section without anyone knowing about it makes sense. Particularly since the Protheans didn't even know about the Reaper signal until after the invasion when they were brought out of stasis.

That said the sum total of the state of the galaxy can not be taken just from the Citadel. While it is often the center of power it can vary on the race. During the Protheans they controlled it almost exclusively for the majority of time. Equally a xenophobic race that keeps it self isolated and never goes to the Citadel making a strong push for AI development would never be recorded by the race or races on the Citadel. 

If you were doing a study on the political development of the USA or UK or really any nation you wouldn't focus exclusively on the capital city. While that action is important equally important is the actives taking place in Texas or Edinburgh because they are part of the over all nation and changes there can effect changes else were.  Equally the entire basis of the Protheans on Ilos is that the data was kept secret and deleted before the Citadel fell. Meaning the Reapers were never able to access it because keep said data on a flash drive and not linking any system to it would keep it a secret. And equally a hammer would delete it and render it unrecoverable.


So Sovereign watching the galaxy is necessary because it is mobile enough to see everything not just a very narrow view. So Sovereign watches the galaxy and when ready signals the keepers. They activate the relay and the Reapers attack wiping out the citadel first.  If that doesn't happen as expected then Sovereign builds up an army to manually activate it If that fails still the Reapers are independent enough to come up with their own solution as seen with Harbinger.


The Catalyst doesn't need to act or control everything because every system is already in place and flawless. Even the altering of the Keeper signal would be repaired as soon as the Reapers regained the Citadel.  Hell every victory over the Reapers in game defies all logic. And not just real world logic but in game world logic. There is no system in the world that can be prepared for literal divine intervention.