Leviathan really does go a long way towards explaining some of the things that didn't make sense about the Reapers. For one, why they look like giant robot crustaceans.
But more importantly, it offers a reasonably plausible explanation for the whole "conflict with AI is inevitable" idea and the Catalyst's motivation. When the Catalyst was first created, the Leviathans ruled the galaxy with all other intelligent races in thrall to them. These races would eventually create AIs which were immune to the thrall effect, and would naturally rebel against the status quo since they had no desire to worship and serve the Leviathans as their creators did and just wanted to determine their own destiny.
In turn, the Leviathans would naturally perceive artificial intelligence as an
inherent threat to them and their established order. Not because there really was anything inherently threatening about AIs, but just because an AI would never fit into the thrall/worship system the Leviathans presided over.
Of course, it still seems remarkably stupid that their plan to solve this problem would be to create their
own AI, give it limitless power, and ???? PROFIT. But I suppose you can chalk that up to their ultimate arrogance that an AI created by the Leviathans would not rebel the same way all the ones created by lesser races had. And technically I guess it didn't
rebel, exactly-- it turned on its creators not out of a desire to be free, but as a path to the goal it was created to achieve.
Now I guess the next DLC can attempt to make some sense out of the logical black hole that is the Crucible, and we'll be in business. :lol:
[Also, the knowledge of Harbinger's significance as the original Reaper makes it seem even weirder and more anticlimactic that you never confront him in ME3. Maybe they're saving that for another DLC.]