User blog comment:The Milkman/The Writing of the Ending/@comment-24174486-20120726200543/@comment-4950455-20120822204440

I have to agree that, at least in the Extended Cut, the Catalyst is not a deus ex machina. Its true nature has very poor foreshadowing, but that nature is pretty much irrelevant to the resolution of the plot.

I think the simplest way to think about it is this: imagine that, instead of the little glowing blue kid, you met another Prothean VI. It doesn't tell you anything about the Reapers' origins, but does outline the same options for using the Crucible.

Is that a deus ex machina?