Through the Mirror
Comes a fate nearer
Than Equestria has ever faced.
The air will be laced
With the blood of heroes as it grows
No light it knows
The greatest will fall
For it has been summoned from evil's call!
Only the soft-spoken
Can heal the very broken
Spirit of the beast,
For all harmony has ceased.
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Yes, ocs are in here, but they are subtle to begin with.

This does have Twilicorn, despite it not being marked in the character selection.