The Season 5 Finale · 3:26pm Nov 29th, 2015
It was...okay...
I mean, it started amazingly! The whole time travel/alt. universe thing was awesome. Yes, Wanderer D said that it didn't make sense because NNM would win every time, but since we saw Luna in the Discord universe, we can assume that someone found the Elements of Harmony, so it kinda does make sense.
I do also have to say that I enjoyed the Sombra bit. The crew to the show always said that he probably would do the most damage to Equestria, and it was nice to see them put their money where their mouth is.
The big issue of it for me was Starlight Glimmer. Her backstory was a little shallow, and it proves that she is dumber than a bag of rocks. Why? Because apparently writing a letter is beyond her! "Wah! I lost my friend cause he moved! Wah!" Hello! The post office! It exists!
But beyond that, I found her redemption to be rushed, and if you're going to rush anything, that's not the thing to rush.
So, yeah. It was okay.
Sombra and the Crystal Empire were rather OP in my point of view. While I can see Sombra making initial gains because Equestria would not have been prepared for war, Equestrian resources and manpower would definitely have tipped the scale sooner or later (that is, if they were willing to use said resources). Even if the Crystal Empire was able to match Equestria's resources and Sombra was a match for Celestia 1-on-1, Equestria has two unparalleled advantages: wings and horns. Approximately 1/3 of the population, and by extension the military, are unicorns who can, at the bare minimum, levitate simple objects such as a sword or bow and arrow which gives them an unmistakable tactical edge. Above all else (no pun intended), there are pegasi who make up another 1/3 and can fly. Air supremacy is a huge strategic advantage as it gives its wielder high mobility as well as improved reconnaissance. Sombra would have a very difficult time fighting against an enemy who could strike anywhere in his empire anytime they wanted. I still liked the scenario and am doing something vaguely similar in my own fic, but I could not help but notice the inconsistencies between pony and human warfare. I suppose it had to retain its TVY rating and female demographic somehow.
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I'm fairly certain crystal ponies aren't all just earth ponies, though.
The big thing Sombra really has going for him is ponypower, though. For the crystal Empire, everyone is in the military, unicorn, earth and pegasus. Any captured ponies are then drafted into his military, meaning he snowballs, the latter of which means, that even if crystal ponies are just earth ponies, then the surprise attack means they've already secured new recruits to combat those advantages.