(spoilers, obviously)
Luna’s magic is weakening and she goes looking for answers. she travels in disguise to one of her old forts and find the bat ponies. they have been living there as the magic protective barrier has been up for a thousand years.
the colony is now in trouble as the shield is weakening.
long story short, the shield is powered by luna but she’s started subconsciously suppressing her magic out of fear of her own power.
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