Grave yards are known to be places where the living pass on into the next life. The place of the dead. But for Twilight, the graveyard is one of the liveliest places in Equestria
After being imprisoned once again for hundreds of years, Discord has had plenty of time to think, and some dark thoughts have had plenty of time to show themselves.
Twilight's an Alicorn, a race that is known to have a lifespan that borderlines eternity. Lucky for her, there's another species that lasts just as long as she does.