She was supposed to sleep away the century's. She was supposed to be unaware of the passage of time and thus maintain her sanity. That was Celestia's plan when she banished her sister for the first time.
But our plans rarely go as expected and nopony could have foreseen what effects a thousand years of pain and solitude would have on the younger princess. Trapped in a cell thousands of miles across, alone except for the most vicious of cellmates Luna struggles to hold on to what tattered threads of sanity she still has.
This is a story about forgiveness, redemption and unimaginable torment. suffered. Of how a broken mare tries to piece herself together when she doesn't even know what is real and what is pure fantasy.