Hi there! I must say I enjoyed reading your story. Perhaps I haven't read enough stories to be bored of an overpowered evil character yet. Yours is the second I've read, so perhaps I'll change my mind. As of now, however, I'm still open for anything.
But let's get to discussion, shall we? (I pay a lot of attention to details, just bear with me there.)
I'll start off with the begin. The very first thing of a book or a story. Titles. It's a good title, don't get me wrong, but I'm focusing more on the titles of your chapters:
- Chapter I First Strike.:
Where's the first strike in this chapter? Is it Phantom breaking free from his prison on the moon or the pegasus overpowering two guards? I guess it kind of counts as a first strike, but I just feel like the title's a bit 'much'.
On a side note, the period isn't necessary in your title.
- Chapter II "Targets":
Quotation marks . . . why? Is it to say these targets aren't actually targets in some form of sarcasm? That doesn't sit right in a title for me. I'd change the title if that were the case. Besides, the target is clear from the start, since you revealed Phantom's plan immediately. The title just doesn't go well anymore.
Second, whitespaces and paragraphs. TL;DR is what it feels like.
Surely I don't want a short story, far from it in fact! But I also need a pause from reading, even if it doesn't mean I'll put the book away. A pause inbetween events in the story and a way to remember what sentence I was reading. Your story's one wall of text, don't do that; reading several smaller bits is more fun than an entire story.
Another thing I'd like to point out is transitions. "THE MOON" and "BACK IN CANTERLOT" to name two.
"Back in, Meanwhile, over in, . . ." should be placed into the storyline itself, not used in transitions. So, change "back in canterlot" to "canterlot" and instead of capitalizing them, use bold text. It stands out more.
A final thing of notice is small. Sometimes you use “ instead of ", in the same spoken sentence, even. Stick with one of the two, unless you want to give a certain character a special feeling to it. (Though that can't be the case in e.g. “Let’s have some fun.".)
Details? Definitely! Inevitable? Absolutely! And I want to congratulate you on this one, you've done a terrific job, barely found any spelling mistakes.
There were some grammatical mistakes and weak sentences e.g. "Trixie stepped back and took her position in front of her troops and behind Phantom and Mira."
"Trixie stepped back and retook her position in front of her troops, behind Phantom and Mira."
took: She went away from her position to attack the manticore. After that, she went back to where she originally was ->
and: Try to avoid reusing words in a sentence (especially 'and') since it's not fun to read.
Definitely not a bad story. It's a little fastforward, which makes me worry how you'll keep this story going for much longer. This is completely up to you, however. I won't force you to write more, enjoy what you're doing and keep it as short/long as you want it to be!
As for Phantom, he has been imprisoned on the moon with Nightmare Moon, then? Well, he was imprisoned 1002 years ago, so he's been there for 2 years and then Nightmare Moon joined him? Couldn't she take him with her when she escaped, or couldn't he do what she did to escape seeing how powerful he is (freeing discord from his prison without the slightest effort, turning Gilda to stone, etc.) or something else? I know he was waiting for a signal, but what kind of signal and what was the reason he decided to escape afterall? I can't find this signal, still. Perhaps I'm just slow, could you explain?
Another thing I've been wondering is why he wants these companions. Trixie and Gilda really seem like they'd slow things down more than they'd be of actual help. Gilda's gone and Trixie needed some sort of gauntlet. Why not give it to someone who could use it to its full potential? I really don't see why you'd do that.
Is Discord even doing anything Phantom's saying, and who is more powerful between the two? Why would Phantom free him if Discord isn't even helping to get to Celestia?
This last thing bothers me as well. No mortal pony stands a chance against Discord and I could imagine he, more than anyone else, would want to get Celestia. If Phantom's more powerful than Discord, why would he even need anyone to help him?
If I'd have to guess, I'd say Luna will have a big part in resolving this crisis considering Phantom's relationship with Luna.
I liked the story itself, but it was weakly presented to me. I hope you improve, so you can give us your story in its full potential. It was a good read, but not so good in reading it.
Don't worry, 5 means I'm indifferent so 6 means I enjoyed it, but it could definitely be improved.
You've done a good job, and I hope I can read the rest of your story soon.