For one thousand years, Equestria has been at peace. Though monsters and threats do sometimes arise, they're typically dispatched in short order, and life goes on. However, several ancient texts and obscure prophecies indicate that this was not always so... and may not always be.
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Equestria, her hills of gold
In dark and mournful times of old
Did once, a hopeless horror hold.
When from her darkest depths did spring