Woww!

That was an interesting story & Im happy that Trixie and Merryweather actually won against the Caribou once again!

I wonder however what was that dark magic near the end?

Did that magic play any role in Twilight's own downfall? considering that Ponyville didn't fall at the time of the raiding and after.

Plus Twilight having most likely magically exhausting herself preparing the defense of Ponyville helped brainwashing her really fast.

[There are numerous spelling errors throughout the text; like autocorrect was doing its work.]
Is that a Dark-Magic virus that incubates within the exhausted capacity of the victim's mana pool? Is that a new detail to FoE? I really like having an explanation for the failure of the resistance; as they fight back using their magic, their own weapon becomes their weakness!
I really can't explain how much I love your writing; it's so... critical?

11357560
11355498
I assume it doesn't like the southern accent of the hillbilly mares.

However, this dark magic in the series isn't really a new detail, but an explanation of an existing part of the setting. As we all know, the Crystal Cock (Heart) was altered by the caribou to turn most stallion and some mares to their side. The question I had to ask myself was "what made the difference between those who were affected, and those who were not". This, added by an FoE fact that the highest percentage of red collars were unicorns, made me think that it was the magic in a pony that could be used to block out the influence, and that unicorns were more vulnerable to it, because what would they do when attacked by a caribou? They would fire off blasts of magic of course.

This tracks for several reasons. as one of the last things Cadence did with her horn was charge the Crystal Heart with her own magic, draining her of most, if not all of it, and Twilight herself was using magic constantly before submitting. Luna, on the other hand, was paralyzed during the invasion by her own guard, so she got to stay black. Now I know what you might be thinking, "What about Sunset Shimmer and Starlight Glimmer?". Well I would think they noticed the problem early, and only used magic in emergencies, in small doses. Levitation is fairly basic, using only a bit of magic, and they only used it to lift a small knife when needed. The small drain might have let a little of the Heart's magic get in, but never enough to overpower them, and after a while, it would get pushed out by there own magic.

So if you are weak magically, or use too much, the enchantment takes over, and you become corrupted. If you have enough magic, and don't use too much of it, then the enchantment gets pushed out, and you'll be fine. In a way, it's the perfect weapon for the caribou. It's just a shame that they themselves didn't understand that's what it was doing, else they would have never de-horned the unicorns.

I see you're putting the idea we discussed to proper use. This was a good chapter and a wonderful set of updates. I look forward to the continuation!