A lot can happen in 20 years. Some things change, some don't. Twilight learns this the hard way after encountering a new villain and waking up 20 years in the future.

Five ponies wander upon the long forgotten royal mountain resort, where it is upon to them to discover harmony and save the spirits of the ponies forever trapped there.

Twilight Sparkle turns evil under the control of the spirit of a long-dead pony