Pups_of_war_76 wrote...
A Deus Ex Machina is a happy ending that is unearned, and therefore emotionally vapid.
An ending in which Shepard and the allied fleet he has been gathering are on the verge of being defeated by the Reapers until a magical, heretofor unheard of fleet of benevolent alien superbeing swoops in to save them is a Deus Ex Machina.
An ending in which the tide is turned by an artifact or technology which required much searching, desperate fighting and sacrifice to recover and ends up being difficult and costly to employ is not a Deus Ex Machina.
No, a
deus ex machina is the unexpected and unforeshadowed intervention of any outside force - the ending that results from it does not need to be happy, it just has to be unexpected, or rather, at odds with virtually everything that had happened up to that point.
The key is
unforeshadowed. If
Mass Effect 3 has us defeating the Reapers with a giant exploding batarian spoon, regardless of the casualties taken or the happiness of the ending, it's a
deus ex machina, because nothing in either of the previous games even hinted that the batarians had a giant exploding spoon that would destroy the Reapers. (Or an ocean of killer shrimp. You get the idea.) If, during the climactic, bloody battle for Earth, the spoon destroys the Reapers along with most of the galaxy, including humanity, then it's still a
deus ex machina despite the fact that lots of sacrifice and fighting happened.
Whereas if the solution to defeating the Reapers involves dark energy, Prothean superweapons, or the technology from the Collector base, then it's not a
deus ex machina regardless of how happy the ending is, because all of that stuff has been foreshadowed in the previous games.