A possible concise summary is:
Twilight Sparkle and her friends try to use the Elements of Harmony to stop Discord, the spirit of chaos, from turning Ponyville into a disaster. However, Discord has corrupted each of them except Twilight, making them act opposite to their true selves. Twilight manages to restore their memories and personalities with a spell, and they join forces to defeat Discord and turn him back into stone. Princess Celestia honors them for their heroism and friendship.
Here are some possible facts extracted from the text:
1. Twilight Sparkle and her friends are trying to stop Discord, the spirit of chaos and disharmony, from taking over Equestria.
2. Discord has corrupted the personalities of Twilight's friends, making them act opposite to their true selves and their elements of harmony.
3. Twilight uses a memory spell to restore her friends' true selves and their elements of harmony: honesty, kindness, laughter, generosity, loyalty and magic.
4. Twilight and her friends use the elements of harmony to defeat Discord and turn him into stone.
5. Princess Celestia honors Twilight and her friends for their heroism and friendship.