Shadow.
Every stallion mare and foal, no matter how bright their smiles or how noble their deeds, casts a shadow.
The saints and the sinners. Zealots and heretics. Poor and wealthy. Thieves and murderers and soldiers and kings. All are joined together by the shadows they cast.
The light covers all with its lies. Shadow serves to remind us of truth within the mendacity of the light.
Behind the dog’s lolling tongue and smiling eyes is the blood of a wolf. And behind the face of every pony there is a shadow. An unseen aspect which they keep secret.
There are no ponies without shadows behind their backs. Just as there are no ponies without secrets. Without sin. Without darkness within their hearts.
We say that we are civilized; we make play that we stand above the slathering beasts trodding through the mud at our hooves. But these are merely the lies we tell ourselves, no more substantial than smoke. Beneath this frail facade of civility, we are but slathering beasts. We burn away the darkness with our lights and fires and pretend that this makes us more than we really are.
But the the brighter our lights burn, the darker our shadows become.