So here's my review of Siege of the Crystal Empire.
So, incase anyone was unaware, I go by the comics as a separate parallel universe to the show, in which Amore's cutie mark is a snowflake instead of a crystalline heart (as told in a book written by Amy Keating Rogers detailing Celestia and Luna's journal), changelings are immune to long falls, and dragons are not immune to lava. (Nightmare Rarity comics, following a completely different style and with Nightmare Moon as a separate entity, I go by as a third alternate reality). Others might disagree but this is my headcanon (though I also heard Meghan McCarthy said so). So, whatever happens in the comics has no influence on anything I wanted to happen or not happen in show canon.
Now for the actual review.
First and foremost, Chrysalis and Sombra in the same scene. Not something likely to be seen in the show as they're both dead (well, Sombra is, Chrysalis is unconfirmed but one is all it takes) and they already played the altered timeline card which had separate futures for Chrysalis and Sombra. These are my two favorite villains and I always say their names in the same sentence. And they talk to each other and fight alongside each other.
Second, Rarity defeats Chrysalis. Aside from being the third unicorn to defeat Chrysalis in comic canon (first two being Shining Armor and Twilight Sparkle, and symbolic because Chrysalis is similar to Voldemort and Lamia who have both killed unicorns), Rarity finally has her shining moment in the comics after all the hell the Nightmare Rarity arc put her through, though like I said I think of Nightmare Rarity as a separate universe from the other comics. Though this is somewhat downplayed by Chrysalis's defeat not lasting long, as well as some being inclined to give Iron Will credit for defeating Chrysalis even though it was Rarity who blasted him into her. Sure, it wasn't Rarity's intention to take out Chrysalis - but it definitely wasn't Iron Will's either!
Third, for the first time in comic history we get a Sombra comic with a light ending. Reflections ended with the good Sombra of the alternate realm being forced to absorb Evil Celestia and Evil Luna's evil and become evil himself, forever corrupting the awesome unicorn we and Celestia knew and loved since they're not likely to go back there. Like, if crystallizing Evil Celestia and Evil Luna had gone smoothly, that would have been a good ending. And Sombra's Fiendship is Magic arc ended with Sombra shattering Amore to pieces and throwing Hope out of the Crystal Empire before making it disappear. Here Sombra reforms - which I was actually hoping for in comic canon, though many hated this even more than his death in the show - and I thought he was going to die there, but Amore saves him then she and the princesses turn him into an actual unicorn. And they set out to restore Amore.
Fourth, the Star Wars reference was cool, no doubt done because of the new Star Wars movie that's out now.
First, cutting short the Chrysalis/Sombra alliance at the beginning of Part 3. Chrysalis and Sombra together was my favorite part of the comic. Yet Part 3 cuts this short, and of course Chrysalis is absent from Part 4. That was a disappointment. (Though they'd have more than made up for it if this had happened by Sombra killing Chrysalis)
Second, the way Chrysalis leaves. In-universe it makes perfect sense that she would fly away, but if they're deadset against killing Chrysalis (and let's face it, to survive both the fall over Canterlot and being blasted by Twilight on two particular occasions, she must be invincible in comic canon. She is literally the Team Rocket of the comics), they could at least imprison her so she's dealt with for the time being but they can use her again if they want to. Seeing as how she orchestrated her escape from two separate imprisonments, one does not simply keep her imprisoned so I'd be satisfied if the comics saw her either turned to stone or imprisoned in Tartarus. Yet here she gets off a karma houdini. In comic canon Chrysalis is the most evil villain because Sombra was more sympathetic and reformed here, Chrysalis is even more evil in the comics than the show as she violently killed a kitten, threatened to kill the Cutie Mark Crusaders, and tried to brainwash Twilight to kill the other Mane 5. And she gets off scot free, probably to take over another kingdom and either kill all its inhabitants or keep them imprisoned forever worse than death. I hate karma houdini like that.
Third, and this is more minor, Iron Will being the choice of villain over someone like Suri Polomare or Tirek. Though he's powerless now, Tirek would make a good evil henchman. Lightning Dust and the Flim Flam brothers I approve, and of course Sombra and Chrysalis I was expecting, but Iron Will is not a villain, at least not in the show.
Fourth, the fact that the power of the Crystal Heart, which is fatal to Sombra, only banished the other Umbrum back to their prison. Like, Sombra is an Umbrum too so if the Crystal Heart kills him, why not the other Umbrum? Did they think they wanted to use them again or are they too afraid to kill even a villain? Aside from Nightmare Moon dying in the Nightmare Rarity arc, Sombra, who is main villain of this comic, died in the show, and nothing in the show brought him back or hinted that he's alive, only the comics. And the comics have less standards than the show because there are scenes in the comics that I know would never have been allowed in the show. Hasbro would approve them destroying the Umbrum, and they don't really have a lot of return value so there was no reason. And this has nothing to do with wanting the Umbrum dead or anything like that, this is about it making no sense, especially since they were realistic to a point of being dark with Chrysalis flying away.
It's a good comic, but far from perfect.